Baby boomers started turning 65 in 2011, marking the unofficialbeginning of their retirement years. The timingcould not have been better for older boomers, who are alreadypart of the wealthiest generation in U.S. history. Since then, thebroad S&P 500-stock index is up 91 percent, includingdividends. U.S. stocks hit a record high yesterday.

Market performance in the early years of retirement is a crucial worryfor anyone living off a nest egg. In the worst-casescenario, stocks crash just as retirees start spending theirsavings, leaving them in a hole they can no longer earn their wayout of.

Older boomers have experienced what is arguably the best-casescenario: The S&P 500 has returned 269 percent since itsMarch 2009 low. As a recent study in the Journal ofFinancial Planning shows, wealthy retirees can be verycautious about spending down their savings. This instinct, alongwith the stock market’s new record, suggests that many boomers arelikely to end up with far more money than they know what to do with.

Researchers followed the spending and investingbehavior of 65- to 70-year-olds from 2000 to 2008. The poorest 40percent of the survey respondents generally spent more thanthey earned, according to the study, which was funded by TexasTech University. Those in the middle were able to keep theirspending at about 8 percent below what they could have safely spentfrom pensions, investments, and Social Security.

The wealthiest fifth, meanwhile, had a gap of as much as 53percent between their spending and what they could have spent. Theauthors wrote:

Retirees in the top quintile of financial wealth were spendingnowhere near an amount that would place them in danger of runningout of money. In fact, the average financial assets of wealthyretirees increased during this period and most retirees spent lessthan their income.

In other words, these affluent Americans retired and thencontinued to get richer. That’s quite a feat when you’re no longerworking, particularly against the backdrop of the mediocre stockmarket of the early 2000s.

It’s not exactly irrational for wealthy people to be cautiousabout spending their money. As financial planner MichaelKitces notes, retirees face many risks: They couldlive longer than expected and then face huge health-care expensesor higher-than-expected inflation. And the market could crashagain.

For now at least, wealthy boomers have a lot more money to spendthan they had any right to expect in the depths of the 2008financial crisis. But that scary experience — and the naturalinstincts to be conservative early in retirement — are likely tohold boomers back from spending their new wealth. Unfortunately,both for the economy and for the boomers themselves, the peoplebenefiting most from the stock market's record high may be themost cautious about enjoying it.

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