By Africa reporter Virginia Gidley-Kitchin

A United Nations conference on stemming the emigration of African professionals to the West has opened in the Ethiopian capital, Addis Ababa.

One of the organisers, the UN Economic Commission for Africa, described the emigration problem, known as the brain drain, as one of the greatest obstacles to Africa's development.

The statistics are scarce but discouraging.

The International Organisation for Migration estimates that 20,000 skilled Africans leave every year for jobs in the West. At the same, time Africa spends $4bn a year on recruiting Western expertise.

Why the brain drain?

A UN report from 1993 said more than 21,000 Nigerian doctors were working in the United States alone, while Nigeria itself suffered from a shortage of doctors.

Those leaving are the very people that African countries need to develop their economies, and once gone, they are unable to pass on their skills to next generation of Africans - a double cost to the world's poorest continent.

But if the problem is well known, its causes are not.

One of the conference speakers, Dr Sibry Tapsoba, who works for a regional research centre in Senegal, said that, surprisingly, most professionals and graduates were not leaving simply to earn more money.

"The first major factor is really the value attached to the contribution of these people. You know that those people who are well trained usually leave because they are persecuted in their own country."

He called for tolerance from African governments.

"We have to facilitate their return. We have to assure the government that everybody who has a PhD is not an opponent," he said.

Encouraging returnees

Experts agree that improving the working conditions for African professionals, particularly scientists, would do much to persuade them to stay.

The IOM has for several years been running a programme (ROQAN or the Reintegration Of Qualified African Nationals) which tries to reverse the brain drain by helping qualified Africans return home on short-term contracts and assisting their reintegration.

But even when this is not possible, Dr Tapsoba said that African doctors or engineers could still make a contribution while working in the West, not just in the traditional way by sending money home, but by using information technology.

For example, he said, they could help colleagues back home without connections to publish their research.