Billionaire Aliko Dangote lost $3.7 billion on June 20 as naira plunged sharply after Nigeria allowed its currency to trade freely without a peg to the US dollar.

Africa’s richest thus fell 25 places in Bloomberg’s billionaires ranking, from 46th on Friday to 71st on Monday.

Dangote’s net worth which is presently valued at $12.7 billion is derived from a 91% stake in Dangote Cement. On Monday, naira tumbled by around 30% to the dollar, after Nigeria’s government decided to allow the currency to trade freely without a peg to the US dollar.

Nigeria was directly hit by the global slump in oil prices. The GDP of this country which derives 70% of its revenues and close to 90% of its export earnings from oil has in fact fell by 0.36% in Q1 2016, Nigeria’s worst performance since the mid-90s.

To strengthen their currency, Nigerian authorities decided in March 2015 to maintain naira’s official exchange rate at N197-199 for a dollar, as Nigeria’s president Muhammadu Buhari considered that depreciating would “kill” the naira.