Africa is undergoing an explosion of wealth as countries open up to the global economy. Many have seen major economic expansions in recent years.

And that’s benefiting a small number of already incredibly wealthy individuals — Africa’s growing contingent of billionaires.

We looked at Forbes’ African rich list from 2011 and compared it to the 2015 list of African billionaires. We stripped out those who hadn’t become billionaires in the intervening four years as well as those whose wealth has declined.

Some of those included will have seen massive increases in the value of things they already own — particularly those that own significant shares in major listed companies. Some will have had their wealth re-evaluated and increased considerably by Forbes.

Take a look at how the richest of the rich in Africa have seen their wealth surge since 2011.