A large crop of House members are likely to retire in the coming months, not necessarily because President Donald Trump is polarizing, the parties are divided, or Capitol Hill is “dysfunctional” — but because 40 years of history tell us it’s going to happen.

Since 1976, 22 House members, on average, have retired each cycle without seeking another office. Thus far this cycle, just five members fit that description: Republicans John J. Duncan Jr. of Tennessee, Lynn Jenkins of Kansas, Sam Johnson of Texas, and Ileana Ros-Lehtinen of Florida, and Democrat Niki Tsongas of Massachusetts.

A full 17 members could announce their decision to walk away from Congress and elected office and the cycle could be described as an average occurrence. Of course, that’s not the narrative that’s likely to build.

If a batch of members announce their retirement, particularly Republicans, much of the media will almost certainly blame Trump, or the infighting within the GOP. Of course, retirement decisions aren’t made in a vacuum and it’s tough to isolate individual circumstances. But the historical context will likely be lost and the psychological impact of one of their colleagues being shot and nearly killed in broad daylight can’t be dismissed.