since Obama became president?

"black" only refers to people of African decent in America. On the Continent of Africa, they are just people.

The majority of Africa is screwed. The majority of countries have absolutely no infrastructure, corrupt military dictatorships, AIDS, or any combination of those three.

The continent itself has the potential to become extremely rich (Diamond and Gold Mines), but they lack the resources and infrastructure to acquire such valuable materials.

Places like Zimbabwe have next to no hope until Robert Mugabe is out of power. Hyperinflation (to the point where the banknote's paper is worth more than the banknote itself), Fascism, and Corruption keep the country from succeeding, and it's almost entirely thanks to Mugabe.

Places like Namibia also lack infrastructure, and with an HIV/AIDS rate at nearly 30% in some areas, it makes it nearly impossible for them to succeed.

Over the past 50 years, Africa has been bad. Numerous military dictatorships have risen and fallen, AIDS has spread, and poverty rates have risen. Africa's not going to change any time soon.

Since Obama has become President.. how has that effected (by changing) the past 50 years in Africa? Is this what you are asking?

EDIT: Oh, well in that case. You make absolutely no sense. The past has already occurred, thus, (unless one considers time travel) cannot be changed. Obama now being the president of the U.S. cannot change Africa's past 50 years of history.

I'm fairly sure that President Obama has not been in office for 50 years....

It really depends on the nation in Africa. It's a continent, not a country.

I think its a very good thing for many reasons.

First, your grammar is lacking something. Second, your question doesn't make sense.