Last year, the fifth of the war, America sent another forty thousand troops to Iraq to halt the rise in violence. So far this surge seems to have worked: the number of Iraqis killed per month has fallen from over three thousand per month a year ago to under one thousand, and American combat deaths have fallen as well, from over one hundred to less than forty per month. Now the extra troops are being withdrawn again. We will see whether those grim numbers bounce back up again, and whether Iraq is any closer to the peaceful, united and pro-Western country that those who planned the invasion so blithely expected. The signs in recent weeks have not been promising.

Even if only temporary, however, the success of the surge is the best news out of Iraq for a long time. Perhaps as a result, America’s debate about Iraq has moved away from the idea of early and complete withdrawal, which was being so hotly debated this time last year. For now, at least, Americans seem resigned to staying in Iraq for a long time to come. They may feel that that costs and risks of staying, though still terribly high, are at least known: the costs and risks of leaving are not.

But are the costs of Iraq known? Behind the headline casualty figures – the United States suffered its four thousandth combat death in March 2008 – lies a huge economic cost which Joseph Stiglitz believes is not at all well understood. Stiglitz is a superbly credentialled gadfly of the economic establishment. A Nobel laureate and professor of economics at Columbia, he served as Chief Economist at the World Bank and chaired Bill Clinton’s Council of Economic Advisors. But in recent books he has stridently attacked the free-market orthodoxies that sanctify globalisation. Now, with Linda Bilmes of Harvard’s Kennedy School of Government, he sets out to tell us how much Iraq costs.