In any event, note that two widely discussed wave elections, 2006 and 1982, do not fall within our definition, nor does an arguable wave election, 2014. In fact, all three just miss a one standard deviation cutoff. In this case, we might just say that the commentariat got it wrong (especially 1982, where half of Republicans’ losses can be chalked up to redistricting), unless people are also willing to accept 1942 and 1954 as wave elections.

I might say, however, that this is only part of the story. There might also be elections that don’t shift things much, but that maintain an unusually strong showing for a party. For example, 1934 did not shift the national balance of power much, but it was still an unusual outcome, historically speaking for Democrats. For this, we turn back to the initial index. Rather than measuring the change in the index, let’s look at elections that result in unusually strong showings for parties, regardless of what their previous showing was.

If we do this, 1936, 1866, 1934, 1868, and 1864 show up as two-standard-deviation wave elections. This makes sense, as the 1860s were a time of generally significant Republican strength, while the early 1930s were a time of generally significant Democratic strength. Expanding to 1.5 standard deviations would cover a few wave elections above, but also add 1964, 1976, and 1862 as “maintaining” elections. Once again, at a single deviation, we add some things that seem to fit our “common” talk, but also exclude a bunch of elections that don’t seem to fit: 1872, 1974, 1958, 1870, 1960, 1912, 1978, 1904, 1940, 1962, 1928 and 1992.