If there was ever a time Nigeria could have taken off, it was in 1999. Democracy had been restored, the country¡¯s economy reopening after decades of mismanagement and plunder under military dictatorships.

Tomi Davies, a systems analyst, was one of thousands of Nigerians who came home to help rebuild the country. After a few years working on public-sector projects, he was offered a bag full of dollars to add ghost employees to the payroll system he was installing. When he refused, a group of men attacked him at his home in the capital, Abuja.

¡°I arrived like many others full of hope, but had to escape in disgust,¡± said Davies, 65, who returned to the U.K. where he is now chief investment officer of Frankfurt-based venture capital firm GreenTec Capital Partners.