I remember from long ago that Michael Moore offered up a critique of the American political system, with him criticizing the rate of retention of legislators. Thinking back to that, I was curious to see what incumbency rates were, and indeed overwhelmingly incumbents are renominated or reelected. I examined the House elections from 1918 to 2020 as these are the years easily available on the Wikipedia pages on these elections. It must be noted that these do not account for instances in which legislators were compelled to retire due to scandal, known unpopularity, or unfavorable redistricting. After viewing these pages and adding up loss of renomination and loss of reelection, I found that from 1918 to 1970, an average of 51 House incumbents lost renomination or reelection. From 1972 to present an average of 24 House incumbents have lost in an election year. Why have I made a distinction between 1918 to 1970 and 1972 to present? 1972 was the first election year the Federal Election Campaign Act was effective, the first modern law regulating campaign finance. The last law of any significance passed on this subject was the 1910 Federal Corrupt Practices Act, which was amended in 1911 and 1925. However, it was a weak law and the 1970 law replaced it.
Critics of campaign finance laws, including conservatives, libertarians, and most notably Minority Leader Mitch McConnell hold that not only do campaign finance laws run afoul of free speech but also serve to protect incumbents. Indeed, incumbency comes with numerous advantages on the Congressional level, including the franking privilege (sending free mail to constituents) and most of the time higher name recognition to start.

This data certainly provides strong correlative backing to this claim. Additionally, if we look at the aftermath of the decision Citizens United, the rate of incumbents who lost rose from an average of 22 from 1972 to 2008 to an average of 30 from 2010 to 2020. While others may offer up explanations as to why some of these years were more turbulent than others (The Great Depression, for instance), the fact stands that even with the huge outlier of 1932 removed from the pre-1972 calculations, the total average is still quite high at 48. Also, in the comparatively calmer post-1970 election years, after the often vilified Citizens United decision incumbents lost an average of 36% higher. The question thus stands to the reader, what do you think makes for better government, one in which more or less incumbents are sent packing?