Russian banks bet in early 2011 that the ruble would eventually fall in value.
Banks earned 73.3 billion rubles ($2.2 billion) in May, or 62.4 percent of their profit for the month, from the weakened Russian currency, according to an expert's analysis.
Having believed as early as the beginning of last year that the ruble would fall in value, banks including major state institutions, and Gazprombank and privately owned Alfa Bank bought other currencies and waited for the ruble to drop, according to a report by Dmitry Miroshnichenko of the Higher School of Economics' Development Center, Interfax reported. The banks apparently bought rubles at the end of May to make a profit on the bet.
In May, the Russian currency fell 12.1 percent against the dollar and 4.9 percent against the euro.
The top three earners from the accurate prediction were Sberbank, which made 10.1 billion rubles in profit from "overvaluation of currency asset values" in May, Gazprombank, which collected 9.9 billion rubles in profit, and Alfa Bank, with 7.9 billion rubles, according to Miroshnichenko's analysis.
The ruble leaped upward against the dollar Friday, standing at 32.55 to the U.S. currency at 5:40 p.m., a change of 1.71 percent, on the back of European leaders' announcement Thursday evening of steps they will take to stem the debt crisis on the continent.
The Russian currency traded at 29.33 to the dollar on May 1 and fell to the level of 33.62 on June 1.