Percentage Change

http://www.census.gov/hhes/www/income/data/historical/household/index.html
Go to the above website, scroll down to Table H2 and select "All Races." Calculate the percentage change in the Shares of Household Income of Quintiles between 1968 and 2012. Notice the dates are in reverse chronological order. Why do you think it has changed in the manner it has? Feel free to visit the main Census page at http://www.census.gov/ and click on Income under People for other interesting facts.