God might not be a gambler, but His creatures certainly are. With the papal conclave due to start on May 7th, punters on Polymarket, Kalshi and Betfair—three prediction markets—have already wagered $19m collectively on identifying the next pontiff. Adjusted for inflation, that is nearly 50 times more than in 2013, when Jorge Bergoglio of Argentina became Pope Francis. It may seem odd that such an arcane process can be forecast at all. But papal betting has a long history. Roman banking houses were taking bets as far back as 1503. Alessandro Damasceni Peretti di Montalto, a 16th-century cardinal, is said to have placed a ten-to-one bet on Francesco Sforza di Santa Fiora, whom he then duly helped to install as Pope Gregory XIV. (Damasceni Peretti had big bills to pay: he is said to have kept a staff of musicians on standby to sing solos at his palace.)

Such shenanigans are presumably a thing of the past. Cardinals say their voting is guided by the Holy Spirit. But today’s bettors look for more tangible clues, such as seniority, diplomatic or pastoral experience and the general direction of the Roman Catholic Church. With millions of dollars on the line, modern markets should estimate probabilities of victory reasonably well—although their current message is that the race is wide open. Our analysis of the odds offered across all three sites finds that even the current favourite, Pietro Parolin, has only a one-in-four chance of election. He is the Vatican’s secretary of state and is expected to preside over the conclave. Close behind him are Luis Tagle of the Philippines and Peter Turkson of Ghana, both of whom would represent regions where Catholicism is growing fastest. Matteo Zuppi, who serves as the Holy See’s peace envoy to Ukraine, is also currently a frontrunner. The markets reserve a healthy 6% chance for a surprise: that someone currently outside the top ten will emerge from the conclave in white. Papability

So far, these odds have been fairly stable. In theory, they should remain so even after proceedings begin. The Church prohibits the 135 electors, “except in cases of proven and urgent necessity”, from any outside contact, on penalty of excommunication. The same applies to anyone else “legitimately present in Vatican City”. The only clue that bettors will get is the number of voting rounds that fail to yield a pope—the outcome of each unsuccessful tally is announced to the world with a stream of black smoke from the cardinals’ burned ballots.

Yet in 2013 the veil of secrecy that gives the conclave its name (from the Latin cum clave, “with a key”) proved surprisingly porous. On the second morning of voting, Giacomo Galeazzi, the Vatican correspondent of Italy’s La Stampa newspaper, reported that Bergoglio, who had not previously been seen as a leading candidate, was near the top of the balloting. Just 34 minutes after the second outpouring of black smoke, Mr Galeazzi posted an update naming the three effective finalists. All were later confirmed to have led the first round of voting.

That year traders on Betfair failed to move on the news. This time, with more money on the line, they might be quicker to act. A sharp shift in our chart once the cardinals are sequestered would be cause for suspicion—though very far from proof—of loose lips in or around the Sistine Chapel.