He was home for two days before the betting question became urgent.
Not urgent in the way of things that required immediate action — he had known since February that the World Cup was in August, had known the draw and the bracket and the results with the specific clarity of eidetic memory applied to things that mattered — but urgent in the way of a window that opened and closed on a fixed schedule regardless of whether you were ready for it.
The fixture calendar had appeared in the Daily Prophet that morning, three columns of fine print beneath a headline about the expanded stadium construction on the Dartmoor site. He read it over breakfast with his mother across the table not quite watching him, and did the arithmetic in his head. The same arithmetic he had done since February, and in Uganda, and on the Portkey home, and it came out the same way it always did.
He was going to need to move quickly. The first group matches were in 6 days. The Goblins would want their own lead time to set the initial lines.
He ate the rest of his breakfast and made a list in his pocket notebook, which his mother had learned to interpret as the signal that he was working through something and would emerge from it when he was done.
Gringotts: sports betting desk. Initial meeting. Establish account appetite.
Below that, the match list of games he knew the outcome of: Transylvania def. England. Luxembourg def. Scotland. Uganda def. Wales. Semi-final: Ireland def. Peru. Final: Ireland def. Bulgaria, 170-160.
And below that, the odds as he expected the Goblins' market to set them. He had spent two afternoons in the Hogwarts library in May reading the back catalogues of Quidditch weekly and the Prophet's tournament coverage from the last three World Cups, building a model of how the Goblins priced fixtures and what a reasonable person who knew nothing would have expected the lines to be. The model was good enough to give him a working framework.
Transylvania were the clear favourites against England but England were England, which meant the market would give them more respect than their actual prospects warranted. One point five to one. Luxembourg and Scotland: Luxembourg slight favourites in a match the market would call close. One point eight. Uganda and Wales: this was the one he had thought about most. Uganda were the African champions, strong and athletic and technically sophisticated in the wand-free tradition he had spent three weeks immersed in. The European betting market, he suspected, would underrate them considerably — the same institutional bias that underrated every non-European magical tradition, the bias he had seen reflected in the absence of Uagadou in the standard Hogwarts curriculum before he had gone looking for it himself. The Goblins' market was sharper than most, but the market-makers were still drawing on a pool of opinion that skewed heavily toward the European and North American teams. Uganda at two to one. He was not going to complain.
Ireland against Peru in the semi-final: Ireland were a known quantity, the current tournament favourites, and Peru were formidable but outmatched. One point five. And the final: Ireland against Bulgaria, 170-160, in a match decided by Krum catching the Snitch in a losing cause. Bulgaria with Krum was as close to a certainty as any single player could make a match. The Goblins would price this nearly even. One point eight for Ireland.
He did the final arithmetic.
One hundred and fifty-one thousand, nine hundred Galleons in the pool, compounded through five sequential bets, all winnings reinvested at each stage: multiplied by one point five, then one point eight, then two, then one point five, then one point eight.
Two million, two hundred and fourteen thousand, approximately.
Fourteen point six times the starting capital and that was just the five matches he was sure of.
He closed the notebook and finished his breakfast.