Why did the Conservatives' large lead in vote shares produce only an 80-seat majority?

Plurality rule voting systems have a well-known tendency to exaggerate the seats of the largest party. A full analysis of the 2019 results remains to be completed, but Tim Smith finds evidence that this time around the Conservatives had a modest 23 seat advantage over Labour in terms of two-party bias. The ‘leader’s bias’ advantage was also much smaller than that which Labour enjoyed in 1997-2005. This may mean that the future boundary reforms to equalize constituency sizes may not be as beneficial as the Conservatives hope.