The repercussions of Lehman Brothers' bankruptcy can still be felt. It has been almost seven years since the firm's failure started a global financial crisis and deep recession in most developed countries. Yet the real damage is only now becoming clear.

Former US Treasury secretary Lawrence Summers says this is the era of secular stagnation, by which he means a slowdown in the gross domestic product growth rate in much of the world. His catchall phrase captures something real, but his focus on real policy interest rates is painfully simplistic. GDP growth is not slower because monetary policy is wrong, but because the crisis revealed, caused or amplified many economic problems.