CHRISTINE LAGARDE, the IMF’s managing director, boasted of a “Washington moment”. At its spring meetings in the American capital this month, the fund saw its lending power almost double, thanks to the promise of $430 billion in loans from more than a score of its members. The official goal is to boost a “global firewall” against crisis. The unofficial hope is that a fatter IMF will help ease fears about the euro, by bolstering the €700 billion ($925 billion) that euro-zone economies have pledged in their own rescue funds.Europeans often simply add the two numbers together, implying there is now a vast $1.4 trillion stash. Not so. Look behind the fat figures and you find a lot of fuzzy maths and wishful thinking—just as worsening news in Spain brings talk of that country needing a rescue (see article).Start with the IMF. Assuming countries make good on their pledges, the money itself is real. The biggest collective contribution will come from the euro-zone countries, which have promised to lend the fund $200 billion between them. Japan is the biggest single donor, with a $60 billion pledge motivated partly by a desire not to be eclipsed by China, partly by fears about its own economic vulnerability. Big emerging economies, such as China, Russia and Brazil, agreed to chip in. Their contribution...