Forbes has released its annual billionaire rankings, with Nigeria’s Aliko Dangote remaining as the continent’s richest man.

His estimated $10.3 billion net worth, however, is nearly $2 billion less than a year ago, primarily due to a roughly 20% drop in the stock price of Dangote Cement, his most valuable asset.

The continent’s second richest is Mike Adenuga, also of Nigeria, worth an estimated $9.2 billion. Adenuga owns Globacom, which is Nigeria’s third-largest mobile phone network, plus oil exploration firm Conoil Producing, extensive real estate holdings in Nigeria and a network of 12,000 cellphone towers. His net worth has climbed dramatically from $5.3 billion in January 2018 as a result of more detailed information provided by him about his assets.

ALSO: 2018 Forbes Highest Paid Hip-Hop Musicians: Jay-Z, Diddy remain at the top

Number three in Africa is diamond heir Nicky Oppenheimer of South Africa. His grandfather founded diamond mining firm DeBeers, which Nicky ran and then sold to mining giant Anglo American for $5.1 billion cash in 2012. He is currently worth an estimated $7.3 billion, down from $7.7 billion a year ago.

In a per country ranking, Egypt and South Africa are tied with five billionaires each, followed by Nigeria with four and Morocco with two. Forbes found one billionaire each from Algeria, Angola, Tanzania and Zimbabwe.

Nigerian cement mogul Abdulsamad Rabiu, who runs and owns the BUA Group, returns to the list for the first time since 2015. He merged his Kalambaina Cement firm into publicly traded Cement Company of Northern Nigeria, which he controlled, in late 2018. Rabiu now owns 97% of the list entity.

Two of the 20 billionaires are women: Isabel dos Santos, the daughter of Angola’s former president, Jose Eduardo dos Santos; and Folorunsho Alakija of Nigeria.