A report put out Friday by by the U.S. Commodity Futures Trading Commission shows hedge fund transactions caused the yen to rapidly strengthen early last week. During the period of Aug. 19-25, hedge funds drastically reduced their sell positions in the yen, the commission's weekly summary shows. The reduction was the largest of its kind in four and a half years.      According to the summary, there were 39,059 contracts to short the yen as of Tuesday. That is a reduction of 51,071 contracts, about $5 billion, from the previous week. The reduction indicates the extent of yen buying during the period was the heaviest it had been since March 2011, immediately after a major earthquake destroyed so much of northeastern Japan.      When the forex market opened in New York on Monday, $1 was trading at 116.15 yen -- the Japanese currency's strongest mark against the greenback in about seven months. The price of the dollar gyrated in a range of 6 yen during the day, when, it is said, hedge funds bought huge piles of the Japanese currency.      Before Monday, hedge funds had been shorting the yen -- a bet that the currency would weaken. Daisuke Karakama, chief market economist at Mizuho Bank, said hedge funds will begin shorting the yen again if the likelihood of a U.S. interest rate hike reappears. Your subscription renewal could not be processed. Please update your payment information to continue enjoying the Nikkei Asian Review.