The Group of 20 was formed eight years ago as the world stared into the abyss of the global financial crisis and recognized that without coordinated action among its top economies, another Great Depression was inevitable. The assembled leaders, which represented about 85 percent of global wealth, 80 percent of world trade and two-thirds of world population, rose to the challenge, pledged to coordinate action to stem the downward spiral, and then, remarkably, honored that pledge. Those policy firewalls kept the Global Recession from becoming a depression.

Ever since, the group has met regularly, producing statements and warnings, but it has not mustered the sense of purpose or urgency that marked its founding. The G-20 has eclipsed the Group of Eight as a global economic manager — understandably, given the limits of the latter — but it appears to increasingly resemble that gathering: more symbol than substance.

Last week's G-20 meeting of finance ministers and central bankers in Shanghai again highlighted risks that threaten the global economy and urged members to undertake the reforms that would insulate them from more shocks. According to the communique released at the end of the meeting, "the global recover continues but it remains uneven and falls short of our ambition for strong, sustainable and balanced growth." Threats to continued growth include volatile capital flows, a sharp fall in commodity prices and the potential "shock" of a British exit from the European Union.