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Wave elections (1918-2016)/Data
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House waves • Senate waves • Gubernatorial waves • State legislative waves |
Competitiveness in State Legislatures |
June 19, 2018
By: Rob Oldham and Jacob Smith
In this report, we compared voter behavior in 50 elections against voter behavior in the most immediate preceding election for the same seats. This means different things for different election groups, which are outlined in the following sections. This analysis does not take into account special elections, appointments, or vacancies that may have occurred between elections.
To see the full range of data used in this report, see this spreadsheet.
U.S. House
The change in the number of U.S. House seats for the president's party is the key variable. It was calculated by taking the difference between the number of seats the president's party won in a given election and the number of seats his party won in the election two years prior. The data comes from Stephen G. Christianson's Facts about the Congress (1996) and the Office of the Clerk for the United States House of Representatives.
U.S. Senate
The change in the number of U.S. Senate seats for the president's party is the key variable. It was calculated by taking the difference between the number of seats the president's party won in a given election and the number of seats his party won in the election six years prior (the last time the same 33 or 34 Senate seats were up). Because U.S. senators were not directly elected on a regular schedule until 1916, making 1922 the first comparable election, this dataset excludes the 1918 and 1920 elections. The data comes from Congressional Quarterly.[1]
Gubernatorial elections
The change in the number of gubernatorial seats for the president's party is the key variable. It was calculated by taking the difference between the number of seats the president's party won in a given election and the number of seats his party won four years or, for states with two-year gubernatorial terms, two years prior. The data comes from Congressional Quarterly.[1]
State legislative elections
The change in the number of state legislative seats for the president's party is the key variable. It was calculated by taking the difference between the number of seats the president's party controlled following a given election and the number of seats it controlled two years prior. All third party and independent officeholders were excluded from this analysis, as were vacant seats, because third party and independent state legislators are rare and unlikely to have a significant influence on the overall data trends. Because of this, the seat share data used in the composite analysis measures the presidential party's share of Democratic and Republican seats, not all seats. All data from 2006 or earlier comes from Michael Dubin's Party Affiliations in the State Legislatures (McFarland Press, 2007). Data after 2006 was compiled by Ballotpedia staff.
Why a quintile analysis?
We identified wave elections by dividing results into quintiles—20 percent groups—and denoting all the elections in the top quintile as waves. A different grouping would have yielded a different definition of a wave election. For example, a quartile analysis would have found that Republicans need to lose 33 U.S. House seats, six U.S. Senate seats, five gubernatorial seats, and 458 state legislative seats for there to be waves in 2018. Looking at the top 10 percent of elections, we would have found that Republicans need to lose 59 U.S. House seats, nine U.S. Senate seats, 10 gubernatorial seats, and 702 state legislative seats.
However, most definitions require some degree of arbitrary choice. The stock market is considered to be a bear market if prices drop 20 percent or more from their 52-week high. It's considered a bull market if the prices are up by 20 percent or more.[2] Not all market observers agree with these definitions, but they are commonly used and give investors a framework to operate within.[3]
We believe that our definition provides a similar framework. We feel justified in our 20 percent definition for wave elections for the following reasons:
- There is no commonly accepted figure used for wave elections. However, if the word wave is to be used, it must be definable for there to be a reasonable discussion about whether one has occurred.
- Historically speaking, wave elections are rare events. By pegging our definition to the top 20 percent of election years, we ensure that wave elections remain distinct from most other election years, even if the president's party loses a substantial number of seats in those too.
- Our study considered 50 election cycles (100 years). Separating the data into 20 percent groups guaranteed that wave elections would be relatively rare but also give us enough information to provide meaningful statistical and historical analysis.
Click here to read the report as one page.
Click here to read or download the report as a PDF.
Footnotes
- ↑ 1.0 1.1 Congressional Quarterly, "Voting and Elections Collection," accessed March 15, 2018
- ↑ The Balance, "How to Recognize a Bear Market," March 12, 2018
- ↑ Seeking Alpha, "The Absurdity of 20% Bull/Bear Market Definition," May 15, 2011
