“The lobby of the Metropole, Moscow's lovingly restored grand hotel a few blocks from Red Square, is almost deserted on this gray spring afternoon. That's just fine with Jeffrey D. Sachs, a boyish-looking 38-year-old Harvard professor who is now probably the most important economist in the world. He has appropriated a cluster of comfortable armchairs for a meeting with two members of his team, Americans who work full time in Russia. The agenda is Russia's safety net or, more precisely, whether unemployed workers will be able to make ends meet. Russia is ...