For much of the past decade, emerging market policymakers were relatively relaxed about the movement of capital across borders. They would cheerily send capital on its way just so long as the entry or exit papers were in order.

The authorities are now a lot more guarded. The 2008-09 crisis was a reminder of the fickleness of foreign investment. Violent currency swings showed the difficulty of dealing with more or less unchecked flows. Central banks have to fight exchange-rate appreciation on the way in, depreciation on the way out.

None has yet gone as far as the Malaysian government of Mahathir Mohamad, which mitigated the impact of the late 1990s Asian crisis by locking foreigners into stocks for a year. But there is growing evidence that judicious controls can tame volatility without threatening the broader economy.