	Introduction

This report provides summary data on the number of Senators and Members of the House who first entered Congress between the 64 th Congress (1915-1917) and the 114 th Congress (2015-2016). Since the convening of the 64 th Congress, 4,201 individuals have entered the House of Representatives for their first, or "freshman," terms as a Representative. An additional 28 have begun service as a Delegate or Resident Commissioner. During th e same period, 844 individuals began their first terms in the Senate. First-term membership is divided into two broad categories in each chamber: Members chosen prior to the convening of a Congress, and those chosen after a Congress convenes. The resulting data, combining pre-convening and post-convening first-term Members, provide a count of all Members who served a first term in the House or Senate. Data on pre-convening first-term Members provide partial insight into the extent of membership turnover in the House and Senate since 1915, and are discussed in greater detail below. Post-convening first-term Member data do not reveal clear patterns within individual Congresses, or over time. This is due in part to the wide range of reasons that a seat in the House and Senate may become vacant in the course of a Congress, and the circumstances under which it may be filled. The data suggest that while there is no consistent pattern of change from Congress to Congress, the overall number of new, pre-convening, first-term Representatives has declined. This appears to be consistent with some academic findings that argue that the durations of Members' careers have been increasing in the past century.
This report provides summary data on the number of Senators and Members of the House of Representatives who first entered Congress between the 64th Congress (1915-1917) and the 114th Congress (2015-2016). First-term membership is divided into two broad categories in each chamber: Members chosen prior to the convening of a Congress, and those chosen after a Congress convenes. The resulting data, combining pre-convening and post-convening first-term Members, provide a count of all Members who served a first term in the House or Senate.
Since the convening of the 64th Congress, 4,201 individuals have entered the House of Representatives for their first, or "freshman," terms as Representatives. An additional 28 have begun service as Delegates or Resident Commissioners. During the same period, 844 individuals began their first terms in the Senate.
Data on pre-convening first-term Members provide partial insight into the extent of membership turnover in the House and Senate since 1915. In both chambers, the data suggest that the overall number of first-term Members elected to Congress who take their seats at the convening of a new Congress has declined since the 64th Congress. This appears to be consistent with findings that argue that the duration of Members' careers has been increasing in the past century. Taken on their own, post-convening first-term Member data do not reveal clear patterns within individual Congresses, or over time. This is due in part to the wide range of reasons that a seat in the House and Senate may become vacant in the course of a Congress, and the circumstances under which it may be filled.