By Patrick Rial

April 10 (Bloomberg) -- Investors turned optimistic for the third time since the credit crisis started last year, gauges of sentiment among individual investors in the U.S. show, a pattern that Helmsman Global Trading says is a signal to sell.

The difference between the American Association of Individual Investors Bull Index and Bear Index surged to 5.6 as of April 2. When the reading rose to 11.5 in November and 13.6 in January it coincided with the end of “bear-market rallies” of at least 21 percent by the MSCI World Index.

“What that’s going to show is that people always want to look at the glass as if it is half full,” said Martin Marnick, head of trading at Helmsman Global Trading Ltd. in Hong Kong. “Using common sense you know what that general trend is. We’re in a recession and this is not the start of a bull market.”

The spread, which has fluctuated between 63 and minus 54 in the past two decades, has climbed above 5 in only three periods since the collapse of Lehman Brothers Holdings Inc. in September. It retreated to minus 8.6 according to data released yesterday.

The AAII gauges are compiled from weekly polls and track whether U.S. individual investors believe the market will rise, fall, or remain unchanged in the next six months. A negative number in the bull-bear spread indicates pessimists outnumber optimists.

The reading fell to as low as negative 51 on March 5, a level not seen since October 1990, when the MSCI World was at the end of a 10-month bear market that erased 26 percent of its value. The MSCI benchmark dropped 59 percent from its October 2007 high to a 13-year low on March 9. It has since rallied 22 percent.

The Organization for Economic Cooperation and Development said on March 27 its 30 members are likely to see their economies contract by 4.2 percent this year.

To contact the reporter for this story: Patrick Rial in Tokyo at prial@bloomberg.net. Last Updated: April 9, 2009 19:56 EDT