Congressional Careers: Service Tenure and Patterns of Member Service, 1789-2021.

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 over time, analyzes factors that affect average tenure in any given Congress, and examines historical patterns of congressional service, including the distribution of years served in each Congress, and the crosschamber experience of Representatives and Senators. During much of the 19 th century, the average tenure of Representatives and Senators remained relatively steady, with incoming Representatives generally averaging between two and three years of prior service in most Congresses, and the Senators averaging between three and five years. Beginning in the late 19 th and through much of the 20th century, average tenure for Members in both chambers steadily increased. Senators' average years of prior service has increased from just under five years during the early 1880s to approximately 10 years in the most recent Congress. Similarly, the average tenure of Representatives has increased from approximately three years during the early 1880s to approximately nine years in the most recent Congress. The average years of service for Members of the 117 th Congress, as of January 3, 2021, when the Congress convened, was 8.9 years for the House and 11.0 years for the Senate. In comparison, the average years of service for Members of the 116 th Congress, as of January 3, 2019, when the Congress convened, was 8.6 years for the House and 10.1 years for the Senate. This report analyzes two factors that 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 do seek reelection. Observed increases in the proportion of Members seeking reelection and decreases in the proportion of Members defeated for reelection align with previous scholarly assessments of congressional history, which conclude that during the early history of Congress, turnover in membership was frequent and resignations were commonplace, and that during the 20th century, congressional careers lengthened as turnover decreased and Congress became more professionalized. The report also examines two further issues related to Member tenure, including the distribution of Member service over time, as well as Members' cross-chamber experience. Although the average service tenure of Members has increased since Congress's early years, a substantial portion of Representatives and Senators in recent Congresses have served for six years or less in their respective chambers. With respect to cross-chamber experience, while a small proportion of Representatives historically have had previous Senate experience, a sizable percentage of Senators throughout congressional history have had previous House experience. [ABSTRACT FROM AUTHOR]

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