Members of Congress are required to disclose their families’ assets and liabilities, excluding their home. The figures for congressional net worth in this story were based on the financial disclosure reports filed for 1984 and 2009.

Members are not required to report precise values for their holdings, but they are required to categorize the values of each asset or liability. The categories are $1,000 to $5,000, $15,000 and $50,000, $50,000 and $100,000, $100,000 and $250,000, etc. The calculations were done assuming that each asset or liability fell at the mean of the category reported.

Assets of less than $1,000, which were reported on some 2009 forms but not on 1984 forms, were dropped from the 2009 to make a better comparison.

For numbers on the wealth of American families, the Post relied on the Panel Study of Income Dynamics from the University of Michigan, a longitudinal panel survey of U.S. families that measures economic, social and health factors over the life course and across generations. Data have been collected from the same families and their descendants since 1968.