Forbes recently released its list of richest persons in Africa for the year 2021. Of the 54 countries African countries, only seven nations have billionaires and the list did not feature women billionaires.

Folorunsho Alakija of Nigeria and Isabel dos Santos of Angola were featured in the 2020 list of billionaires from Africa. However, the 2021 publication did not feature them because they fell below the $1 billion benchmark per the calculation of their wealth.

Alakija, according to Forbes, is Nigeria’s richest woman. She is the vice chair of Famfa Oil, a Nigerian oil exploration company with a stake in Agbami Oilfield, a prolific offshore asset.

Her first company was a fashion label whose customers included the wife of former Nigerian president Ibrahim Babangida. In 1993, she was awarded an oil prospecting license which was later converted to an oil mining lease.

Forbes notes that Alakija’s worth dropped below $1 billion due to the coronavirus pandemic which affected oil prices. In March 2020, oil prices dropped to levels not seen before since 2002 due to a drop in demand for crude oil amid COVID-19. The fall in crude prices affected the monies accrued to her from her oil field.

Isabela, on the other hand, fell below the billionaire line as a result of a series of court actions freezing her assets in both Angola and Portugal. In 2020, she was charged by Angola’s attorney general with embezzlement and money laundering.

Since 2013, Forbes named her as Africa’s richest woman worth an estimated $3.5 billion. Her father was the longtime former president of Angola and it is believed that she made her wealth because of her father’s influence. Her father ruled Angola from 1979 to 2017.

Forbes calculated her wealth by assuming she has no access and likely little chance to gain back control of the frozen assets—together worth about $1.6 billion if not frozen. Prior to the latest publication, her estimated worth was $2.2 billion

Forbes names Nigeria’s Aliko Dangote as the richest person in Africa with an estimated worth of $12.1 billion, up by $2 billion from last year’s list thanks to a roughly 30% rise in the share price of Dangote Cement, by far his most valuable asset. The second richest is Nassef Sawiris of Egypt, whose largest asset is a nearly 6% stake in sportswear maker Adidas.

The biggest gainer on the list is another Nigerian cement tycoon known as Abdulsamad Rabiu. He, together with his son, owns 97% shares of BUA Cement PLC, which listed on the Nigeria Stock Exchange in January 2020. Shares in BUA Cement doubled the past year, pushing his fortune up by an extraordinary 77%, to $5.5 billion.

According to the Forbes list, South Africa and Egypt each have 5 billionaires; Nigeria has three while Morocco has two. Collectively, the 18 billionaires from Africa are worth $73.8 billion, a little more than the $73.4 billion aggregates worth of the 20 billionaires on last year’s list of Africa’s richest people.

Forbes’s methodology of calculating African billionaires includes those who reside in Africa or have their primary business there. Based on this methodology, the list excluded Sudanese-born billionaire Mo Ibrahim, who is a U.K. citizen and billionaire London resident Mohamed Al-Fayed, an Egyptian citizen.

“We calculated net worths using stock prices and currency exchange rates from the close of business on Friday, January 8, 2021. To value privately-held businesses, we start with estimates of revenues or profits and apply prevailing price-to-sale or price-to-earnings ratios for similar public companies. Some list members grow richer or poorer within weeks-or days-of our measurement date,” according to Forbes.