Ten years ago, the world’s richest countries accounted for a significant majority of the globe’s economic activity. But the pendulum is swinging in the other direction, according to the Organization for Economic Cooperation and Development.

A new O.E.C.D. report finds that rich countries and poor countries now each contribute about an equal share of the global economy. And by 2030, developing countries will account for 57 percent of world G.D.P.:

“[T]he economic and financial crisis is accelerating this longer-term structural transformation in the global economy,” according to a release from the agency.

The projections are based on research on economic growth by the late Angus Maddison, who tried to model world G.D.P. numbers going all the way back to Year 1.