The U.S. Senate, Seniority, Term Limits, and Legislative Productivity

After the dust died down from the 2010 elections, I wanted to try and put what had happened into some broader historical perspective--especially where the Senate was concerned. As we know, the Senate is supposed to be the saucer cup that cools the "hot passions" of the House (said George Washington). Only 1/3rd of U.S. Senators are up for election in a given campaign cycle, so the chamber should provide more stability. Sure enough, turnover doesn't happen as much in the Senate in a given cycle--it takes many elections to have a lot of turnover in the upper chamber.

But we have had, in rather quick succession, three such elections: 2006, 2008, and 2010. A fair number of Senate incumbents lost in each election. I wondered: how much turnover had happened during this period and was it outside the historical norm? Finally, what might the implications be of a relatively less experienced and junior Senate?

I examined three pieces of data: the average time of years of service in the Senate at the beginning of each session, the percentage of members who were new to the chamber, and a rolling average (that is, the percentage of members who were serving their first term during a six-year period). The first chart shows in a bar graph the average term of service in each Senate session from the 104th through the 112th Congresses. The second chart shows both the percentage of new members in the chamber and the rolling average over the same period.

First, Senate careers. Note that they have been getting longer, on average, but the 112th Congress does NOT represent the low point in the time series. The 105th Congress does. The election of 1994, of course, brought in many new members but the 1996 election was almost as transformative: there were 16 open Senate races in that cycle alone. Replacement can happen not only through elections, but through death and retirement--and many senators chose to leave in the 1996 Congress. This, combined with the electoral earthquake of 1994, brings the average time of service down to about less than eleven years. This number then creeps up to more than 13 in the 111th Congress (an all-time historic high), which then drops sharply in the 112th Congress--the result of some long time incumbents losing.

The 2010 elections do represent a high point for the number of new members entering into the chamber with 16 percent of the members new to the Senate. This is slightly higher than the 105th Congress, which consisted of 15 percent new members. What is really striking, however, is the fact that over the last threeCongresses (the 110th, 111th, and 112th) 36% of the membership is new to the Senate. That's the high point during period examined.

What does all this new blood mean? Empirically, it should mean less legislative productivity. The one thing we know from studies of congressional careers is that members with more seniority and time in service tend to produce/write more legislation (see the work of John Hibbing for more specifics). Constituent service actually tends to remain rather stable over a member's career, but the true benefit of all that experience appears to be legislative expertise, success, and productivity. One possible consequence of term limits is, simply put, a legislative branch that does less legislating. We might expect, then, that the 112th Congress will be relatively less productive when compared to its immediate historic counterparts.

How does the 112th Congress stack up against other historic congresses in terms of turnover? I took another slice of Congressional history: the 89th through the 97th Congresses. This represents a period of some electoral turbulence: the 1966, 1974, 1978, and 1980 elections were particularly hard on incumbents. I did the same analysis as above for length of service and the percentage of new members in the chamber.

During the late 1960s and the 1970s, members generally served shorter careers than today. However, a series of elections and retirements brought the average time of service from 10.56 in the 90th congress to merely 7.43 in the 97th Congress (which began in 1981 during Ronald Reagan's first year in office)!

This final chart shows why: incumbents were devestated by the elections of 1974, 1976, 1978, and 1980. What is striking is how few incumbents returned after the 1978 election. Many were defeated in primary and general elections, but many also chose to retire voluntarily. The 1976, 1978, and 1980 elections had brought in more freshman to the Senate than any election between 1994 and 2010. The culmulative effect was, by the time the 97th Congress showed up for work in 1981, more than half of the Senate were serving in their first term.

Why was there so much more turnover during the late 1970s? The answer is not retirements. If you look at retirements in 1976, 1978, and 1980 and compare them to retirements in 2006, 2008, and 2010, approximately the same number of senators retired (22 versus 20). The real difference is senators losing reelection: far more were defeated in the late 1970s than now. This might suggest that the incumbency advantage has actually strengthened in the Senate over time. Or, perhaps the desire for change among the electorate was greater in the late 1970s than now?

In any case, we can conclude the following:

1. The 2010 election, in the Senate, did bring more turnover to the chamber when compared to recent elections.

2. The amount of turnover, however, is not especially high when compared to other historic periods.

3. Incumbency is still a powerful electoral force and, contrary to what one might think, its power seems to have increased in the Senate over time as demonstrated by the number of incumbents losing reelection in the late 1970s when compared to a similar period today.