The papal conclave, in which cardinals gather in the Vatican for a closed-door meeting to select a new pope, begins today. If past conclaves are any indication, they'll have made their decision by the end of the week. But that's a relatively recent trend; conclaves used to be much, much, much longer.
Most papal conclaves since 1846 have lasted only two or three days, five at most, according to some impressively detailed data analysis by the Atlantic Wire's Philip Bump. He has several charts worth checking out, but this one is particularly interesting. It shows the length of every conclave since 1455; in other words, how long it's taken for the cardinals to pick a pope.
For centuries, it seems, the process of selecting a new pope could take months. And why shouldn't it have? The institution exercised enormous political and financial power in Europe at the time. The cardinals' maneuverings and negotiations were an extension of notoriously contentious and complex European politics that had so much at stake in the outcome. The elections, it seems, were not just about determining the church's leadership. They were about politics, both of the back-room and great-power sort, a combination that could make the conclave even trickier.
The longest conclave of the past five centuries was in 1740, which took six months. Six months! Imagine if we didn't have the result until September, watching the Vatican every day for 180 days in a row for that mysterious white smoke to appear. That election was not even the longest, though: three in the 13th century lasted more than a year each, with one of them lasting from 1268 to 1271.
The pope's decline in hard power, around the early 19th century, also seems to coincide with the shorter conclaves. Since then, they've been typically brisk affairs. But that might also have to do with rule changes, as Bump points out.