Abstract
Legislative turnover is indicative of political careerism, district competitiveness, and the strength of the incumbency advantage. Although there are many examinations of legislative turnover in U.S. state legislatures, there has not been an update in nearly 2 decades. One limitation of the existing turnover measures is the inability to distinguish between naturally occurring turnover and the artificial turnover caused by term limits. In this research note, I present an update to legislative turnover from 2002 to 2018 and discuss the importance of using updated data, as well as avenues for future research.
Turnover is influenced by a number of different factors including institutional rules and electoral restrictions (François & Grossman, 2015; Matland & Studlar, 2004; Maestas, 2000; Rosenthal, 1974; Shin and Jackson III, 1979), and is used to assess phenomena including electoral stability and legislative capacity (Moncrief & Thompson, 2001; Uppal & Glazer, 2015; Woods & Baranowski, 2006). More recent research utilizes turnover levels to help understand gender and minority representation within the legislature (Arceneaux, 2001; Darcy & Choike, 1986; Reingold, 2012, 2019). Turnover is associated with legislative careerism (Habel, 2008; Moncrief et al., 2004), legislative behavior (Kerby & Blidook, 2011; Kirkland, 2014; Uppal & Glazer, 2015), and even has ties to democratic legitimacy (François & Grossman, 2015). Measures of turnover are also routinely used as a control in studies of the state legislature where turnover is not the primary interest (Maestas, 2000; Makse, 2019; Melusky, 2018; Stonecash, 1999; Shay, 2020).
Legislative turnover is typically a measure of the number of seats vacated each year or session. The turnover measure presented by Moncrief et al. (2004) is commonly used by scholars to examine the causes and effects of turnover, but the data end in 2002. Since the implementation of term limits in 15 states, this measure turnover is no longer representative of what is occurring in the legislature. In this research note, I update legislative turnover from 2002 through the 2018 election. I present two different measures of turnover, one which takes into account the artificial turnover caused by term limits. In addition to presenting the average rate of turnover for all 50 states, yearly data will be made publicly available. I discuss the use of each measure of turnover and present a brief replication analysis before discussing avenues for future research.
Updating Turnover
Studies Where Turnover is the Primary Interest.
Historical Overview of Average Turnover Rates.
Note: States in italics currently have legislative term limits. * Historical data are from Moncrief et al. (2004).
The average rate of turnover for all states from 2000 to 2018 is 13% in the lower chamber and 11% in the upper. Moncrief et al. (2004) found that from 1991 to 2000, the average rate of turnover was 23% in state senates and 25 in the lower chambers, and only six states had an average below 15% (2004, 365). This update reveals that the average rate of turnover decreased in 98 of the 99 state chambers from the 1991–2000 period to 2002–2018. In some instances, like Alabama and New Mexico turnover declined by more than 25%. Even in states that have legislative term limits, there is a noticeable decline in the average rate of turnover.
Using an out of date measure of turnover can lead to incorrect assumptions about what is occurring in the legislature. There was very little change in the average turnover rate from 1981 to 1991, which is likely why the latter measure is still used to examine turnover. This update demonstrates an evident decline in turnover with the average of all states dropping by more than 10% and a total of 36 states have an average turnover rate below 15%. Over time, turnover has continued to decline, and the Moncrief et al. (2004) measure is no longer an accurate indicator of turnover in the states.
The Two Types of Turnover
There are two types of turnover that occur in state legislatures, natural and artificial, which collectively make up the total turnover rate. Naturally occurring turnover is the expected rate of turnover that is a result of election loss, resignation, and even retirement. These natural causes of turnover are a result of a lawmaker pursuing a career in the legislature and making her own career choices. Different from natural turnover, artificial turnover is a result of forced turnover that removes the ability of a legislator to make her own decision. In the U.S. context, artificial turnover is a direct result of having legislative term limits where many lawmakers are forced from office and are unable to make that decision for themselves.
This idea of two forms of turnover is not new. After the passage of term limits, Francis and Kenny (1997) noted that there would eventually be different types of turnover as a result of term limits. Even though term limits have been in place for 20 years in some states, the differences in legislative turnover have remained largely unexplored. Artificial turnover exists in only 15 states and implies that legislators were not given the choice to return and, instead, were forcefully removed from office because of term limits. In contrast, natural turnover is present in all states as members cycle through the legislature.
Average Percent of Turnover by State, 2002–2018
Note: States in italics currently have legislative term limits.
Figures 1 and 2 illustrate the differences that exist between total and natural turnover. A darker block indicates a higher rate of turnover. In Figure 1, the darkest shaded states are all those that have term limits, aside from New Hampshire.
3
However, in Figure 2, there are very few states that are dark. In fact, term-limited states like Nebraska, California, and Louisiana appear to have lower turnover than other non-term-limited state like Kansas, West Virginia, and North Carolina. Overall, these two figures illustrate that there is a noticeable difference between the two measures of turnover. Average rate of total turnover in all states, 2002–2018. Average rate of natural turnover in all states, 2002–2018

Why is it necessary to have two distinct measures of turnover? Including or excluding the artificial turnover caused by term limits can bias results. Ultimately, theory will drive the decision to use one form of turnover over another. When measuring turnover, it is important to ask if the goal is to assess the number of people leaving the legislature or the different reasons why individuals leave. Studies that utilize turnover as a predictor for large-scale behavior ought to consider the theoretical implications of looking at all turnover versus natural turnover.
Using one measure in lieu of another can result in theoretical bias. In some instances, including the artificial turnover caused by legislative term limits can inflate results, especially when looking at career motivations, legislator representation, or policy responsiveness. It would be inaccurate to include artificial turnover if turnover were being used to examine constituent satisfaction with their legislators. In other examinations of turnover, the focus will be on how many people are leaving, regardless of why; in this instance, the total rate of turnover is sufficient.
To illustrate the differences between the two types of turnover, I replicate part of Todd (Makse, 2017) analysis of state legislative committee retention. 4 His analysis is centered on evaluating the effects of committee retention on bill referrals and passage rates in 13 states, five of which have term limits. For replication purposes, I follow his analysis of bill referrals (Table 3, page 429). Makse utilizes a measure of observed turnover in the legislature to help account for overall stability within the legislature. While Makse’s use of observed turnover is valid for his theoretical argument, it is possible that there could be an alternative theory to account for those states that have term limits.
Replication of (Makse, 2017) Committee Bill Referrals (Table 3).
*** p < 0.01, ** p < 0.05, * p < 0.1
Centering the analysis on those legislators who have the opportunity to stay yields different results than when looking at the overall rate of turnover. When accounting for those legislators who have the opportunity to continue serving, turnover no longer conditions the relationship between committee retention and bill referrals. This replication emphasizes the importance of how theory and data must align. The theory must drive which measurement of turnover ought to be used. In some circumstances, it might be of use to estimate models using both measures to better understand how the forced turnover in states without term limits affects the results.
Discussion and Suggestions for Future Research
Since early examinations, legislative turnover has been utilized as a key explanatory variable for everything from economic conditions to legislative behavior. Current measures of turnover do not capture the historically low levels of turnover present in U.S. state legislatures. This update, through 2018, produces a more accurate measure for scholars to use. In addition, there is a secondary measure that accounts for the artificial turnover that is caused by term limits.
The differences found between this measure and the Moncrief et al. (2004) measure point to the question of how often must turnover be updated? While there was little variation from 1981–1990 to 1991–2000, there was a great deal of change from 1991–2000 to 2002–2018. These shifts suggest an update is essential at least every two decades. It appears unlikely that a major shift would occur in as little as a 10-year span, given that lawmakers are increasingly serving for lengthier periods of time.
The continued decline in legislative turnover in U.S. state legislatures indicates that incumbents remain secure and new members rarely enter office. These data can be used to examine the driving factors behind the continued low rate of turnover, as well as the implications for these rates. The two measures here can be used in different capacities based on the theoretical underpinnings of turnover. In some instances, the inflated rate of total turnover can bias results, especially when evaluating legislative careerism and the decisions that members must make. The difference between natural and artificial turnover may be less important in the examinations of policy responsiveness or legislative efficiency because it matters how many lawmakers are leaving the legislature but matters less why they are leaving.
Future avenues of research include exploring the reasons for the continued decline in legislative turnover. Has turnover declined as a result of fewer people running for office or is it because members are choosing to serve for longer, and what are the differences between these internal and external forces? There is increasingly more focus on demographic turnover; there needs to be more research on the variation of legislative diversity and whether these lower turnover rates are particular to any one group of lawmakers. Last, it is worth exploring the point at which turnover rates become too low and there are not enough new members bringing forth new ideas. At what point does the lack of turnover hinder policy development and ultimately harm the institution?
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
