Over the past few decades, the American public has become more socially liberal on most issues. It has reversed its opposition to gay marriage and marijuana legalization and grown unsupportive of the death penalty. But there’s one issue that’s effectively stagnated, evenly dividing the electorate, with no signs of budging: abortion.

Twenty years ago, 56 percent of the country favored legal abortion. Today, that number is 57 percent, with minimal fluctuation over the past two decades.