By Adam Haigh and Whitney Kisling -  Nov 14, 2011 4:38 PM GMT+0800/ Bloomberg/  U.S. companies are buying back the most stock in four years, taking advantage of record-high cash levels and low  interest rates  to purchase equities at valuations 15 percent cheaper than when the credit crisis began.

Corporations have authorized more than $453 billion in repurchases this year, putting 2011 on track for the third- highest annual total behind 2006 and 2007, data compiled by Birinyi Associates Inc. show.  Warren Buffett’s  Berkshire Hathaway Inc. (BRK/A)  bought shares for the first time, and  Amgen Inc. (AMGN)  sold debt to fund its buyback. U.S. companies spent 70 percent more on their stock last quarter than a year ago, according to financial filings as of Nov. 11.

Market bulls say the rise shows executives are confident the  U.S. economy  will avoid a recession. While the Standard & Poor’s 500 Index peaked the last time buybacks were this high, companies in the gauge are generating three times as much cash, price-earnings ratios are lower and 10-year Treasury yields are around 2 percent, data compiled by Bloomberg show. Bears say the increase means companies lack better uses for capital.

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