Literature Review (USPS Financial Crisis)

Annotated Bibliography: USPS Financial Sustainability

Christian O. Ogbebor

Nova Southeastern University

RES-8200

Professor Su

June 21, 2026

Annotated Bibliography: USPS Financial Sustainability

Article 1: Balaz, M., Vaculik, J., & Corejova, T. (2024). Evaluation of the impact of the Internet of Things on postal service efficiency in Slovakia. Economies, 12(10), 271. https://doi.org/10.3390/economies12100271

1. Problem being studied: Postal companies around the world are experiencing a drop in volume and increase in operating costs. This study aimed to investigate how the application of Internet of Things (IoT) technologies can make a significant contribution to the efficiency of postal services and contribute to the mitigation of the economic pressures resulting from structural revenue loss.

1. Purpose of the study: The purpose of the study was to quantitatively assess the impact of the IoT adoption on operational efficiency of postal services in Slovakia and to provide an empirical support material for technology-based reform strategies which can be used in postal services facing financial difficulties.

1. Theoretical framework: The study was based on production efficiency theory using the Cobb-Douglas production function to explain the production of output as a function of various inputs. In this framework, the authors were able to examine the marginal impact of the use of IoT as a capital input on postal productivity.

1. Participants/data units: The Slovak postal system was used as the unit of analysis. The data analyzed included panel data for Slovak Post company for several fiscal years, with the indicators of IoT adoption, output indicators, and cost data as the key data sources.

1. Data collection instruments: Secondary quantitative data were obtained from Slovak Post annual reports, databases of the national telecommunications regulatory authority and Eurostat postal statistics. These data sets were used to build regression models with Cobb-Douglas specifications.

1. Methods: This study adopted quantitative research design with regression analysis using Cobb-Douglas production function model. The level of IoT adoption was measured by a composite score that was queried and regressed into efficiency indicators such as processing speed, delivery accuracy and cost per unit of mail processed.

1. Findings/results: There was a significant positive effect on postal service efficiency from the use of IoT. The authors calculated that for every 10% increase in the integration of IoT, the per-unit processing costs measured by the authors could be reduced. Therefore, they claimed that technology investment is a viable option to help offset the decline in revenue. The authors, however, warned that the situation will not change because of IoT without structural financial changes to the business models.

1. Evaluation: It is a well-designed quantitative study published in a peer-reviewed MDPI Journal. The methodologically appropriate use of the Cobb-Douglas framework is appropriately used, and the regression analysis is clearly presented. An important constraint is that research results are only valid for a smaller-scale postal environment (Slovakia) and significantly different from that of the USPS. The study is better at teasing out technology effects than at considering the policy aspects of financing universal service.

1. Relevance to planned research: This study is directly applicable to the USPS research problem because it offers empirical evidence that technology adoption can benefit the efficiency of postal operations, which is one aspect of a multi-faceted approach to reforming USPS's financial sustainability.

Article 2: Blagojevic, M., Sarac, D., & Mostarac, K. (2023). Selecting the flexible last-mile delivery models using multicriteria decision-making. Promet - Traffic & Transportation, 35(5), 635-654. https://doi.org/10.7307/ptt.v35i5.292

1. Problem being studied: The last mile of postal delivery chains is the most expensive and accounts for a high percentage of the entire postal expenditure. The choice of the optimal delivery model for the last-mile delivery is a key operational challenge for USPS and other postal operators that are seeking to increase package delivery service revenue to counter loss of mail revenue.

1. Purpose of the study: The goal of the study was to propose and implement a structured multicriteria decision making (MCDM) model to systematically rank and select the flexible last mile delivery models for postal operators, which can be used as an empirical tool for optimizing the cost-revenue balance in package delivery operations.

1. Theoretical framework: This study was based on the theory of multicriteria decision analysis (MCDA) and the theory of optimization for supply chain. The MCDA framework assumes that complex organizational decisions that involve the assessment of several competing criteria (such as cost, speed, reliability, and environmental impact) must be made by systematically weighing and scoring them, instead of optimizing them with respect to a single criterion.

1. Participants/data units: It was carried out in the context of a European postal operator. The evaluators in the MCDM process were expert postal logistics managers and operational planners. The expert panel gave weights to the criteria and then scored the alternative delivery models based on each criterion.

1. Data collection instruments: A structured expert judgment instrument was used to elicit criteria weights from the panel. Last mile delivery operational performance data were sourced from the postal operator's internal reporting systems and publicly available logistics benchmarking data.

1. Methods: The study adopted the quantitative MCDM design technique of Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method. Last-mile delivery models were compared with composite scores across various operational and financial metrics. A sensitivity analysis was performed to evaluate the stability of the ranking.

1. Findings/results: Hybrid delivery models—those that integrate the role of postal carriers with crowdsourced delivery workers—were the most promising solution for flexible last-mile delivery in terms of cost efficiency, delivery speed and reliability, and scalability, according to the MCDM analysis. The fully outsourced models did not fare well in terms of reliability and the in-house models did not fare well in terms of cost. The results have direct significance for postal operators such as the United States Postal Service (USPS) who wish to be competitive in the package delivery business without having to pay proportionately higher wages.

1. Evaluation: The study is very well designed and organized. The TOPSIS based MCDM is proper and well validated technique to solve the type of multi attributes decision problem. One drawback is that the expert panel was quite small, possibly causing subjectivity to the weighting of criteria. The results should be further validated to test their generalizability in different postal labor market environments, such as the heavily unionized environment at the USPS.

1. Relevance to planned research: This study is of interest to the USPS research problem because it provides an empirical framework to assess delivery model alternatives that directly inform the operational reform options available to USPS as it seeks to increase package revenue and contain the labor cost that is the USPS's largest financial expense.

Article 3: Borowiec, L. (2021). Direct subsidies and compensation funds in financing of universal postal services. Entrepreneurship and Sustainability Issues, 8(3), 545-564. https://doi.org/10.9770/jesi.2021.8.3(34)

1. Problem being studied: For national postal operators with a universal service obligation (USO), all postal addresses must be covered without regard to profitability. The basic issue is the financing of the net cost for universal service when the market alone is unable to support it, a problem directly relevant to USPS's self-funding mandate with no congressional appropriation.

1. Purpose of the study: The study sought to test two main possible mechanisms for financing universal postal obligations in the EU member states empirically and draw implications from the financial sustainability of each of them.

1. Theoretical framework: Both public goods theory and regulatory economics theory were adopted in the study. The USO was described as a quasi-public good, a product that markets systematically underprovided, which led to the public provision of this good. The analysis of the compensation fund design and the market-distortion risks of each financing mechanism were based on the theory of regulatory economics.

1. Participants/data units: The postal regulatory systems and financing mechanisms of all EU member countries were examined. The empirical foundation was derived from reports of national regulatory authorities, European Commission postal market studies and databases from the Universal Postal Union (UPU). The national postal regulatory framework was the unit of analysis.

1. Data collection instruments: Secondary data were gathered from the Annual Reports on the Development of the European Postal Market published by the European Commission, UPU World Postal Union databases and national postal regulatory authority annual publications in the EU member states.

1. Methods: The study used a comparative institutional analysis that integrated quantitative financial analysis of USO net costs and qualitative institutional framework analysis. The cross-national comparisons were organised around an analytical framework which was applied in the same way in each member state's postal sector.

1. Findings/results: The study concluded that direct government subsidies offered greater money certainty and stability to postal operators, however, they also brought the risk of market distortions and dependence on government. Compensation funds were more market consistent but were also more complex to administer and were challenged in court by other carriers. The study found that hybrid financing approaches, which blended aspects of both financing options, and tailored to the institutional and market conditions, provided the strongest foundation for achieving financial sustainability for universal service.

1. Evaluation: This is a well-done comparative study that uses a good analytical framework, and has an adequate data sourcing. It has the major advantage of the cross-national comparison that it provides across the EU systems. The restriction on its USPS applicability is that EU regulatory and legal frameworks vary significantly from that of the U.S. institutional framework, including a ban on direct appropriations by the USPS.

1. Relevance to planned research: The study is particularly timely for USPS research since it directly tackles the core financing issue that the USPS faces: how to provide universal service without a sustainable funding mechanism, and offers internationally tested policy options for Congress to consider.

Article 4: Drab-Kurowska, A., & Budziewicz-Guzlecka, A. (2021). The digital post ecosystem: Example of Poland in the context of research. Sustainability, 13(5), 2701. https://doi.org/10.3390/su13052701

1. Problem being studied: The digitization of communications has changed the business model of the postal sector radically, with the demise of physical letter mail and the rise of electronic channels. The dilemma for postal operators is to deal with the rapid growth of revenue decline from traditional mail, while building a sustainable digital service portfolio to help them counter the losses.

1. Purpose of the study: The purpose of the study was to conduct an empirical analysis of the structure and dynamics of the digital postal ecosystem in Poland, as well as to assess the possibilities of the postal operators' portfolios' strategic repositioning from physical to digital postal services for their long-term financial sustainability.

1. Theoretical framework: The theory used for the study was the digital ecosystem theory and the theory of business model innovation. In the digital ecosystem theory, the postal operator is seen as one node in a digital service network, where value is created through different interoperability and service complementarities as opposed to individual product delivery.

1. Participants/data units: Poczta Polska (Polish Post) was chosen as the main case subject, as well as having comparative references on other postal operators from the European Union. Poczta Polska annual reports, the Polish Office of Electronic Communications regulatory databases and the surveys on the postal market conducted by the European Commission were sources of empirical information.

1. Data collection instruments: Secondary quantitative data consisted of mail volume statistics, digital service adoption rates, and revenue diversification data based on regulatory filings. The qualitative data related to strategic positioning was obtained from official documents of the postal operator and market analyses from the regulatory authorities.

1. Methods: The study used mixed methodologies – quantitative (trend analysis of financial and volume data of the post) and qualitative (content analysis of strategic planning documents). The analysis tracked the trajectory of physical mail volume decline and the growth of revenue that is derived from digital services over a multi-year period.

1. Findings/results: The study revealed that the Polish postal operator has done good work to get going with the creation of a digital service ecosystem, such as e-document delivery and digital government service intermediation, but that digital revenue is not yet sufficient to offset the losses of physical mail revenue. The authors found digital transformation to be not a sufficient answer for postal operators to become financially sustainable without reducing its cost base, mostly through reductions of fixed cost components, like infrastructure and employment, related to obligations of universal physical delivery.

1. Evaluation: The study is well-structured, data is presented clearly and the methodology used is sound, and it thus provides a good analysis of the dynamics of digital transformation in a postal landscape in Europe. The major constraint to its applicability for USPS is the scale and regulatory context of the US and Poland, and the lack of in-depth study of the USO financing mechanism.

1. Relevance to planned research: This study has implications for the USPS research problem because while digital transformation is essential, it is not enough to be a financial sustainability strategy on its own; this study provides empirical evidence to support this argument that USPS needs a structural business model reform beyond the adoption of technology.

Article 5: Ittmann, H. W. (2023). The postal performance of the South African Post Office: An international and local perspective. Journal of Transport and Supply Chain Management, 17, a948. https://doi.org/10.4102/jtscm.v17i0.948

1. Problem being studied: Structural financial problems are visible in postal operators around the world, where the losses of letter-post services have resulted in a decrease in services and in the costs of the universal service obligation.Postal operators worldwide are facing structural financial problems due to the decline in letter-post services and the burden on the costs of the universal service obligation, as well as due to competition from private logistics operators. The South African Post Office (SAPO) is a case study of these systemic issues to which an acute form of financial failure is found in this institution.

1. Purpose of the study: The purpose of the study was to test the financial and operational performance of SAPO in comparison to international postal operators from the Universal Postal Union (UPU) sample, as well as to measure the position of SAPO in relation to the postal performance patterns observed globally, and to determine the structure of the causes of postal financial decline.

1. Theoretical framework: The Universal Postal Union (UPU) Integrated Index on Postal Development (2IPD), was used as an analytical organising framework in the study. Under 2IPD, the performance of postal operators is measured in four areas: reliability, reach, relevance and resilience, offering a common framework for comparing financial and operational sustainability.

1. Participants/data units: The South African Post Office was the main unit of analysis, and records from the UPU 2IPD were used to form a sample of postal operators from 170 countries. Financial and operational performance information is for several fiscal years.

1. Data collection instruments: Primary data instrument was the Universal Postal Union's 2IPD database, which was complemented by South African postal regulatory authority publications, South African annual reports as well as documents from the Universal Postal Union's World Postal Strategy.

1. Methods: This study adopted the quantitative comparative analysis design. The 4 index dimensions were compared to the international peer postal operators in SAPO and trends were analysed by looking at how SAPO's performance has developed over time. Operating ratio, revenue per delivery point and letter volume decline rates were added in.

1. Findings/results: The study revealed that SAPO was one of the worst performing postal operators in the world according to the 2IPD composite index, especially on the reliability and resilience index. International comparisons also showed that the reduction of volume in letter-post is a common factor behind the deterioration of all postal financial structures, and that postal operators that have not diversified their revenue sources or reformed their cost structures have suffered the most significant financial losses. The study found the USO's fixed delivery cost to be a key structural blockage to financial recovery.

1. Evaluation: It is an empirical study that is very rigorous, and conducted on an internationally standardized measurement framework, and so its findings are further comparable and generalizable. Specific institutional and macroeconomic conditions in the USPS (difficulties with infrastructure, political governance) are not directly comparable with SAPO, thus making transferability from case to case somewhat limited.

1. Relevance to planned research: This study is directly referenced in the USPS problem statement and offers the cross-national empirical support for the idea that letter-post decline is a systemic phenomenon that is global in nature, as well as a catalyst for the financial crisis of the postal sector in the US, which suggests a need for systemic, as opposed to incremental, solutions.

Article 6: Ittmann, H. W. (2023). Postal digital transformation dynamics: A system dynamics approach. Systems, 11(10), 508. https://doi.org/10.3390/systems11100508

1. Problem being studied: Operators of postal services are presented with a complicated and nonlinear transformation problem, trying to control the simultaneous decline in the traditional postal service and the increase in new digital and logistics services. The issue is that linear planning models are not suitable for considering the feedback processes, which shape the financial sustainability of the postal sector in this transition.

1. Purpose of the study: The purpose of this study was to create and use a system dynamics model to simulate the financial and operational dynamics of postal digital transformation, and offer a quantitative tool for examining the impact that various reform strategies can have on the long-term sustainability of postal operators.

1. Theoretical framework: This study was theoretically based on the system dynamics theory developed by Jay Forrester. Unlike regression or static models, system dynamics offers a model for studying complex, feedback-related systems over time and the reinforcing and balancing feedback loops that occur. It's applied to postal systems to model the feedback mechanism between loss of volume, cost pressure, service cuts, and additional volume loss.

1. Participants/data units: It was based on the UPU data and studied a representative sample of postal operators in 73% of the postal sector worldwide. This international postal operator dataset has been used to parameterize the system dynamics model.

1. Data collection instruments: The main empirical data were obtained from the postal statistics databases of the UPU. The model was built and simulated using system dynamics modelling software (Vensim). Model structure and parameter values were expert-elicited from postal sector experts.

1. Methods: The study adopted a mixed methods design of quantitative modeling of system dynamics and qualitative model validation by experts. The model simulated postal system behavior under various postal system reform scenarios: diversification of services (digital) to postal services, cost structure reform, and regulatory reform. Model robustness was tested with sensitivity analysis.

1. Findings/results: The simulation results showed that a postal system with continuing letter-post decline moves into a self-reinforcing decline loop unless structural intervention takes place: volume declines lead to a decline in revenue which then leads to cuts in postal services, which lead to a further reduction in volume. Digital diversification was proved to be not enough to escape this vicious circle. The model revealed that simultaneously implementing cost structure reform, revenue diversification and USO financing was needed for the financial stability of the system.

1. Evaluation: This is a methodologically innovative study that seeks to fill a real gap in the research on postal sectors, using system dynamics to a problem that is in essence dynamic, with feedback. The main constraint is the abstraction of the model, as system dynamics models are based on assumptions that might be different from the institutional constraints in a given country. The structural validity of the model is supported by the international data basis and expert validation, however.

1. Relevance to planned research: This study is cited explicitly in the USPS problem statement, and forms a framework for a systems-level empirical framework that supports the argument that USPS's financial crisis can only be solved if the USPS is structurally changed, directly informing the case for comprehensive structural reform.

Article 7: Jovanovic, B., Sarac, D., & Cacic, N. (2024). Performance benchmarking of European postal incumbents with TOPSIS and BMW-TOPSIS. Utilities Policy, 91, 101797. https://doi.org/10.1016/j.up.2024.101797

1. Problem being studied: There is a wide range of financial and operational results for national postal operators in Europe, despite their largely identical universal postal services frameworks. Currently, there is a lack of rigorous comparative performance benchmarking to help policymakers and regulators identify best practice and structural determinants of postal financial sustainability.

1. Purpose of the study: The purpose of the study was to design and implement an empirical benchmarking framework that can be used to measure and analyze the financial and operational performance of the postal incumbents in Europe, and to identify institutional and operational features that are linked to better financial sustainability results.

1. Theoretical framework: The research approach was based on the benchmarking theory and efficiency frontier analysis. Benchmarking theory states that performance comparisons with best in class reference points offer performance improvement targets. The study took it one step further by incorporating multi criteria weighting to reflect the multi-dimensionality of postal performance.

1. Participants/data units: The sample consisted of postal incumbents in Europe that are obligated to provide universal postal services. The data on financial performance, operational efficiency and service quality were obtained from national postal regulatory authority (NPR) annual reports and the statistical database of Universal Postal Union (UPU).

1. Data collection instruments: The quantitative secondary data were gathered from the postal market reports of the European Commission, publications of national regulatory authorities and postal statistics of the UPU. The weights of the criteria for the benchmarking framework were obtained through a structured expert judgment process.

1. Methods: Two MCDM techniques were used in the study: the standard TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) and a new Best-Multiple Weights extension (BMW-TOPSIS) that includes expert-weighted criteria. Rankings were calculated on financial, operational and service quality dimensions and sensitivity analysis was performed to determine the stability of the ranks.

1. Findings/results: The benchmarking results showed that despite the similar regulatory environment, the performance gap is a very wide one across the European postal incumbents. Higher revenue diversification ratios—especially those from logistics and e-com services—and more flexible labour costs structures had a significant impact on the financial performance rankings of operators. Operators with high share of fixed labor costs and a high reliance on market dominant mail revenues scored lowest on financial sustainability measures.

1. Evaluation: It is a good empirical study with a clear methodological contribution in the BMW-TOPSIS extension that deals with a known weakness of the traditional TOPSIS in dealing with uncertainty in the weights of criteria. A major shortcoming is the use of secondary data which may be subject to different national accounting systems, which could limit cross-national comparisons. The study is comparable with Blagojevic et al. (2023) in this bibliography concerning the use of the MCDM methods for the postal operational problems.

1. Relevance to planned research: The results of this study are very relevant to the USPS research problem because the benchmarking results empirically show that revenue diversification and labour cost flexibility are the two major structural drivers that determine postal financial sustainability and directly inform the USPS reform dimensions that need to be addressed.

Article 8: Morales Sarriera, J., & Schwartz, A. E. (2021). Strategies to reduce postal network access points: From demographic to spatial distribution criteria. Utilities Policy, 69, 101175. https://doi.org/10.1016/j.jup.2021.101175

1. Problem being studied: Postal operators with extensive networks of physical stores and access points have high upfront costs. The rationalization of the postal network may provide savings, but the rationalisation of postal access may lead to an inequitable reduction in service on access points, most of which will be in rural and low-income areas where the need for postal access is greatest.

1. Purpose of the study: The objective was to define and test in an empirical way new rationalization options for post networks in Italy based on criteria other than the demographic approach, checking which one minimizes the reduction of inequitable access and maximizes cost saving.

1. Theoretical framework: The study was based on the theories of spatial equity theory and public service rationalization theory. Spatial equity theory suggests that geographic distribution of public services should reflect population distribution, and that cuts which exacerbate the inequity in access should be penalized. The trade-off between cost efficiency and service equity was evaluated by using the normative approach of public service rationalization theory.

1. Participants/data units: The Postal network of Italy (Poste Italiane) was the level of analysis. The data set included geographic and demographic information for all municipalities in Italy and the entire Poste Italiane post office location data. A set of GIS spatial analysis tools was used on the combined dataset.

1. Data collection instruments: The main instruments were Geographic Information System (GIS) spatial data such as municipal boundary data, population density data from the Italian National Statistics Institute (ISTAT) and Poste Italiane data on the location of post offices. Distance to network was calculated using GIS analysis.

1. Methods: The design of this study was an approach of quantitative GIS based spatial analysis. Two alternative network rationalization scenarios were modeled: one that called for closing offices in municipalities with population size thresholds; and one that called for having a minimum geographic coverage. A quantitative estimate of the cost savings and equity effect under each scenario was performed.

1. Findings/results: The spatial distribution approach proved to be as effective as the demographic approach in terms of cost savings and access to services, but much more effective in terms of access equity, especially in rural and mountain areas. The study found that only demographic-based rationalization criteria disproportionately affect geographically isolated communities. The spatial approach significantly decreased the equity effect of network downsizing by 40% at the same level of cost savings as the demographic approach.

1. Evaluation: This study examines spatial analysis methods with a strong policy relevance in a methodologically rigorous way. This GIS application is replicable in an analytical framework that can be directly applied to USPS post office network rationalization planning. This limitation is country-specificity, in that the geographic and demographic distribution in Italy is different to that in the U.S. and so is the calibration to be applied.

1. Relevance to planned research: The USPS physical retail network is one of the largest cost centers, and this study offers an empirically validated approach to minimizing the inequitable harm that such a rationalization of postal access networks may cause to the rural, low-income communities that have been cited as the key stakeholders in the USPS problem statement.

Article 9: Pamucar, D., Dobrodolac, M., Simic, V., Lazarevic, D., & Gorcun, O. F. (2025). An interval rough improved ordinal priority approach-based decision support system to redesign postal and logistics networks. Technology in Society, 80, 102774. https://doi.org/10.1016/j.techsoc.2024.102774

1. Problem being studied: The challenge of optimizing a postal and logistics network for a situation of low budgets and high demand volatility demands optimization of multiple conflicting objectives such as minimizing costs, maintaining service levels, and ensuring fairness of access. Traditional optimization techniques, which are based on single criteria, are not suitable for this complexity.

1. Purpose of the study: The study was set to design and empirically test a new multi-criteria decision support system based on the interval rough improved ordinal priority approach (IR-IPA) technique to assist in the decision making process for the postal and logistics network redesign under financial constraints and uncertainty.

1. Theoretical framework: The study was based on the theories of decision support systems and rough sets. Since the postal network planning process involves uncertain future demand, uncertain cost trends and uncertain regulatory conditions, rough set theory is a suitable mathematical tool to deal with imprecise and uncertain information in decision-making situations.

1. Participants/data units: The empirical validation has been done by taking the case subject as a postal logistics operator from Europe. Network configuration data, cost data, and service coverage metrics were provided by the operator. Preference data developed by a panel of postal logistics experts were used for the multicriteria weighting process.

1. Data collection instruments: Operational data of the case postal operator's network management systems and expert judgment instruments for criteria weighting were used. The IR-IPA algorithm was programmed into computer software and used on the combined data set.

1. Methods: The quantitative decision science methodology (rough set interval analysis and the ordinal priority approach) was used in the study. Several Network Redesign Options were considered for the following factors: Operating Cost, Service Coverage, Delivery Time, and Carbon Footprint. The IR-IPA ranking was robustly checked by comparing with other MCDM methods.

1. Findings/results: The IR-IPA decision support system resulted in less rank reversal in sensitivity tests and more stable rankings of network redesign alternatives when compared with the conventional MCDM methods. The recommended network configuration obtained by empirical tests to reduce the operating costs was found to provide service coverage above the prescribed minimum, but with a reduction of 18%. The study clearly showed that structured multicriteria decision support can help determine network configurations which are financially sustainable without degrading the service in a proportional manner.

1. Evaluation: It is a technically high-level study that represents a real contribution in the area of methodology as a new approach to postal network decisions, based on the rough set theory. The main constraint is the difficulty of the implementation of the IR-IPA approach, which could be a barrier for postal planners who lack analytical skills. This study provides the most sophisticated decision analytical framework, but is less accessible to direct policy application than the studies presented by Blagojevic et al. (2023) and Jovanovic et al. (2024) in this bibliography

1. Relevance to planned research: The study is pertinent to the USPS research problem as it describes a validated decision support model for designing a postal network under financial constraints, which can be directly applied to the current USPS network consolidation initiatives, which are part of the Delivering for America strategic plan.

Article 10: Rogowski, J. C., Gerring, J., Maguire, M., & Cojocaru, L. (2022). Public infrastructure and economic development: Evidence from postal systems. American Journal of Political Science, 66(4), 885-901. https://doi.org/10.1111/ajps.12594

1. Problem being studied: Although the infrastructure of the postal system is a key determinant of economic development, there is limited causal empirical evidence on the link between capacity of the postal system and local economic outcomes. The economic impacts of the erosion or failure of the postal system have not been properly measured, making it difficult for policymakers to make evidence-based decisions about postal investment and reform.

1. Purpose of the study: The study was designed to provide sound causal empirical evidence of the link between the investment of the postal infrastructure and the local economic development, as well as to identify the economic development value of postal systems through historical natural experiments and panel data methods.

1. Theoretical framework: The study was based on two theories: public infrastructure theory and the institutional economics of state capacity. Based on public infrastructure theory, communication infrastructure diminishes transaction costs, enhances market integration and promotes economic coordination, thus having measurable effects on economic development. The authors employed the natural experiment of historical variations in the investment of postal infrastructure.

1. Participants/data units: Two different empirical data sets were employed in the study. The first, a cross-national panel data set of postal infrastructure and development indicators in countries from the 19th century to today. The second was a U.S. county-level panel dataset, which combined historical U.S. Census postal investment data with the results of county-level economic outcomes over the period 1850-2007.

1. Data collection instruments: Historical postal data from the U.S. Census, such as the number of post offices, postal revenue, and mail volume by county were correlated to various economic development indicators, such as per capita income, population density, and manufacturing output. Cross-national data came from UPU historical databases and national statistical archives.

1. Methods: The study adopted the quantitative panel data design with difference-in-differences estimation and instrumental variable methods to estimate causal effects of the investment in postal infrastructure on the economic indicators. These approaches enabled the authors to overcome potential selection bias issues by using variation in the timing and location of infrastructure investment which was likely exogenous to local economic conditions.

1. Findings/results: The study identified strong positive causal relationship between the provision of postal services and economic development of the area. Economy, population density and manufacturing development rates were significantly higher among counties with higher levels of postal investment than among similar counties with lower levels of investment. The cross-national analysis was done to ensure that the results remained valid when controlling for other institutional characteristics and demonstrated that countries with more robust postal systems had more favorable economic development results. The authors projected that the economic impact of the loss of postal services would be great and enduring on communities affected.

1. Evaluation: This is the most methodologically sophisticated study in this bibliography, appearing in a prestigious political science journal which has high standards for causal identification. This is a good example of a policy research question for which best practice causal inference methods include difference-in-differences and instrumental variable approaches. One drawback is that it is based on historical data, which might not accurately reflect current e-commerce and digital communication dynamics. The causal model and results of the study, however, are very relevant to ongoing USPS reform discussions in the United States.

1. Relevance to planned research: This study is a component of the USPS research problem, because it offers the best causal evidence of the economic development benefits of postal infrastructure, offering direct quantification of the economic costs of potential service reductions or failures if the USPS deteriorates financially, and especially to rural and low-income communities who are identified as key stakeholders in this context.