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 equalise constituency sizes may not be as beneficial as the Conservatives hope.