Congressional Careers: Service Tenure and Patterns of Member Service, 1789-2015 [January 3, 2015] [open pdf - 523KB]
"The average service tenure of Members of the Senate and House of Representatives has varied substantially since 1789. This report presents data on Member tenure and a historical analysis of tenure trends. […] Two underlying factors appear to influence variation over time in the average years of service for Members of Congress: the decision of sitting Members whether or not to seek election to the next Congress, and the success rate of Members who seek election to the next Congress. In addition, short-term variation in average service is affected by the individual service tenures of Members who do not return for the following Congress. […] The report also examines two further issues related to Member tenure. First, the distribution of Member service that underlies the aggregate chamber averages is examined. Although the average service tenure of Members has increased, more than half of Representatives and Senators in recent Congresses have served eight years or less. Second, the report analyzes historical trends in the percentage of Members who have served in both chambers. While only a small and declining proportion of Representatives have historically had previous Senate experience, throughout history a sizeable percentage of Senators have previously served in the House."
CRS Report for Congress, R41545