(See Corrections & Amplification below.)

A month ago I visited Kibera, the largest slum in Africa. This suburb of Nairobi, the capital of Kenya, is home to more than one million people, who eke out a living in an area of about one square mile -- roughly 75% the size of New York's Central Park. It is a sea of aluminum and cardboard shacks that forgotten families call home. The idea of a slum conjures up an image of children playing amidst piles of garbage, with no running water and the rank, rife stench of sewage. Kibera does not disappoint.

What is incredibly disappointing is the fact that just a few yards from Kibera stands the headquarters of the United Nations' agency for human settlements which, with an annual budget of millions of dollars, is mandated to "promote socially and environmentally sustainable towns and cities with the goal of providing adequate shelter for all." Kibera festers in Kenya, a country that has one of the highest ratios of development workers per capita. This is also the country where in 2004, British envoy Sir Edward Clay apologized for underestimating the scale of government corruption and failing to speak out earlier.

Giving alms to Africa remains one of the biggest ideas of our time -- millions march for it, governments are judged by it, celebrities proselytize the need for it. Calls for more aid to Africa are growing louder, with advocates pushing for doubling the roughly $50 billion of international assistance that already goes to Africa each year.

Yet evidence overwhelmingly demonstrates that aid to Africa has made the poor poorer, and the growth slower. The insidious aid culture has left African countries more debt-laden, more inflation-prone, more vulnerable to the vagaries of the currency markets and more unattractive to higher-quality investment. It's increased the risk of civil conflict and unrest (the fact that over 60% of sub-Saharan Africa's population is under the age of 24 with few economic prospects is a cause for worry). Aid is an unmitigated political, economic and humanitarian disaster.