Last week the National Institute of Economic and Social Research, a British think tank, released a startling chart comparing the current slump with past recessions and recoveries. It turns out that by one important measure -- changes in real G.D.P. since the recession began -- Britain is doing worse this time than it did during the Great Depression. Four years into the Depression, British G.D.P. had regained its previous peak; four years after the Great Recession began, Britain is nowhere close to regaining its lost ground.