Stock splits, enticements to investors in bull markets fordecades, have been pushed to the brink of extinction by chiefexecutive officers still recovering from the 2008 financialcrisis.

Four companies in the Standard & Poor's 500 Index splittheir shares this year and 16 did in 2011, down from an average of35 from 2004 through 2007 and a fraction of the 102 in 1997, datacompiled by S&P and Bloomberg show. The disappearance of splitsless than five years after stocks began their biggest plunge sincethe Great Depression underscores changing behavior by CEOs as wellas individuals who haven't returned to equities.

“There's a reluctance to split a stock after such a decline isstill fresh in the collective memory of management,” said DougRamsey, the Minneapolis-based director of research at LeutholdGroup LLC, which oversees about $3.5 billion. “A stock split isjust an accounting mechanism, but the psychology behind it is,you're not going to do it unless you're confident you're going totrade at an elevated level.”