There are still four and a half months to go before the presidential election. But there’s a vote next week that could matter as much for the world’s future as what happens here: Britain’s referendum on whether to stay in the European Union.

Unfortunately, this vote is a choice between bad and worse — and the question is which is which.

Not to be coy: I would vote Remain. I’d do it in full awareness that the E.U. is deeply dysfunctional and shows few signs of reforming. But British exit — Brexit — would probably make things worse, not just for Britain, but for Europe as a whole.

The straight economics is clear: Brexit would make Britain poorer. It wouldn’t necessarily lead to a trade war, but it would definitely hurt British trade with the rest of Europe, reducing productivity and incomes. My rough calculations, which are in line with other estimates, suggest that Britain would end up about two percent poorer than it would otherwise be, essentially forever. That’s a big hit.

There’s also a harder to quantify risk that Brexit would undermine the City of London — Britain’s counterpart of Wall Street — which is a big source of exports and income. So the costs could be substantially bigger.