The IMF and World Bank were both established after the second World War. Dubbed the "Bretton Woods twins" after the New Hampshire resort where they were born in 1944, both institutions have, in the intervening period, often been in competition and have had a mixed bag of results.

The objectives of both when they were created were very different, but in more recent years there has been some overlapping. The mixed success of both institutions is leading to calls for a new structure; the existing one, after all, was conceived in a very different era, without free capital flows and with fixed exchange rates.

The World Bank started out as a lender primarily dealing with post-war reconstruction in Europe and infrastructure projects in the developing world. The Fund was central to the Bretton Woods fixed exchange rate regime, supporting countries with balance of payments difficulties. The Bank's lending was long-term and structural and the Fund's short-term and macro economic.

But by the mid-1970s, as fixed exchange rates were abandoned, the Fund found that industrialised nations no longer had any need for it and both began lending to less developed economies.

Eventually after a series of public rows, the mandates were redefined. The Fund was given primary responsibility for economic surveillance and exchange rate matters, balance of payments and growth oriented stabilisation policies and instruments. The Bank is responsible for the composition and appropriateness of development programs and priorities, operating in the less developed world.

This has worked reasonably well up to now. But the Asian crisis, which neither institution has succeeded in stemming, has led to fresh calls for at least a partial merger or the creation of joint departments and even the abolition of one of the institutions.

This is likely to be the focus of much of the debate at their annual meetings in Washington next week.