The candidate who won the popular vote in the US has not won the presidency four times in the past two centuries, most recently in 2016. This column uses state-level voting data in presidential races extending back to 1836 to examine just how likely these Electoral College inversions are. The findings suggest that in 45% of presidential races decided by less than one percent of the vote, the popular vote winner will lose. Over the last 30 years, the probability has been about 70% that if an inversion occurs, it would have been a Democratic popular vote majority but a Republican Electoral College win.