Main Street and Wall Street are moving in opposite directions. Individual investors are plowing money back into the U.S. stock market just as professional strategists say gains for this year are over.

About $100 billion has been added to equity mutual funds and exchange-traded funds in the past year, 10 times more than the previous 12 months, according to data compiled by Bloomberg and the Investment Company Institute.

The growing optimism contrasts with forecasters from UBS AG to HSBC Holdings Plc, who say the stock market will be stagnant with valuations at a four-year high. While the strategists have a mixed record of being right, history shows the bull market has already lasted longer than average and individuals tend to pile in at the end of the rally.

“If Wall Street, after poring over all known data, comes up with a target and we’re already there, and you still see individual investors buying and they’re typically the ones that are late to the party, it would seem there is limited upside,” Terry Morris, a senior equity manager who helps oversee about $2.8 billion at Wyomissing, Pa.-based National Penn Investors Trust Co., said in a July 8 phone interview.

U.S. stocks slid from record highs last week, sending the Standard & Poor’s 500 Index to the biggest drop since April, amid concern over financial stress in Europe and the timing of higher U.S. interest rates. The Chicago Board Options Exchange Volatility Index jumped 17 percent from a seven-year low.

Steady Gains

The S&P 500 is still up 6.5 percent for 2014, compared with a 3.5 percent advance in the Bloomberg Commodity Index of 22 raw materials and 3.3 percent gain for the Bloomberg U.S. Treasury Bond Index.

For most of this year, equity investors have seen little volatility and steady gains, giving them confidence to put money back into the market. Individuals deposited about $9.5 billion in June to stock funds and have added cash in eight of the past 10 months, data compiled by ICI and Bloomberg show. That’s a reversal from the five years through 2012, when $300 billion was withdrawn.

Blue Skies

Professional investors, such as Nick Skiming of Ashburton Ltd., say that individuals investors are attracted to stocks after seeing others getting rich from a big rally, a time when equities are usually overpriced. The bursting of the technology bubble in March 2000 was marked by mutual funds absorbing a record $102 billion in the first quarter.