Caucus crunching

Since 1972—as I’m sure the world is by now sick of hearing—tonight’s caucuses in Iowa have been the first major electoral event on the road towards the US presidency. As I type, media on both sides of the Atlantic are in a mild frenzy of speculation as to who will win in each party, and how much the result will matter. Perhaps most famously, Jimmy Carter won more votes than any other Democratic candidate in 1976, effectively launching what became a successful presidential campaign. But how many times has an out-and-out Iowa winner gone on to lead the free world?