Policymakers, including finance ministers and central bank governors, are as entitled to have holiday wishes as much as anyone else. But they should be careful with their wish list. Sometimes the law of unintended consequences leads to unexpected and undesirable side effects.

The expansion of domestic financial markets can promote economic growth through a more efficient allocation of savings and other mechanisms.  Foreign participation in these markets can contribute to their development in several ways. Foreign investors, for example, can provide more liquidity that leads to lower yields. Shanaka Pereis found that a 1% increase in the share of foreign investors in government bond markets in ten emerging markets led to a decrease of about 6 basis points in the yield on those bonds. All this suggests that capital flows benefit financial markets.

But larger financial markets can also bring unanticipated consequences. After Federal Reserve Chair Ben Bernanke spoke last spring of tapering the Fed’s asset purchases, the exchange rates of many emerging markets depreciated while their central banks used their foreign reserves to slow the changes. Barry Eichengreen and Poonam Gupta have investigated these reactions. They find that the magnitude of the changes in exchange rates and reserves were linked to the size and openness of a country’s financial markets. They interpret this as evidence that foreign investors rebalanced their portfolios in those markets with the most largest and liquid financial systems. They conclude that “success at growing the financial sector can be a mixed blessing.” Financial regulators need to be ready for the volatility that increased capital flows can bring along with all their benefits.