One of the phenomena of the last several decades has been the rise of the individual investor. As Americans have become more responsible for their own retirement, they have poured money into stocks with such faith that half of the country’s households now own shares directly or through mutual funds, which are by far the most popular way Americans invest in stocks. So the turnabout is striking.

So is the timing. After past recessions, ordinary investors have typically regained their enthusiasm for stocks, hoping to profit as the economy recovered. This time, even as corporate earnings have improved, Americans have become more guarded with their investments.

“At this stage in the economic cycle, $10 to $20 billion would normally be flowing into domestic equity funds” rather than the billions that are flowing out, said Brian K. Reid, chief economist of the investment institute. He added, “This is very unusual.”

The notion that stocks tend to be safe and profitable investments over time seems to have been dented in much the same way that a decline in home values and in job stability the last few years has altered Americans’ sense of financial security.

It may take many years before it is clear whether this becomes a long-term shift in psychology. After technology and dot-com shares crashed in the early 2000s, for example, investors were quick to re-enter the stock market. Yet bigger economic calamities like the Great Depression affected people’s attitudes toward money for decades.