Are you fed up with stocks yet? The answer from American investors is a howling yes.

They've been fleeing from stocks this summer, yanking $16.1 billion from stock mutual funds in June and July. They added $50 billion to bond funds, according to the Investment Company Institute.

Now, some St. Louis investment gurus fear that investors are making a classic mistake: buying bonds high and selling stocks low.

Investing in bonds rather than stocks is "the mistake of your life," says Joe Terril, who manages $420 million at Terril & Co. in Des Peres. "You're going to get your brains beat out."

That's not a universal view. Bonds do pay interest, even if rates are chintzy, while stocks may sink deeper if the economy stays weak.

"Investors are being rational. They're going for something that's real, rather than hope," says Juli Niemann, analyst at Smith Moore & Co.

It's easy to see why stock investors are disgusted. Just look what they've been through.

The S&P 500 index of big-company stocks lost about 15 percent of its value, including dividends, over the past 10 years. By contrast the JP Morgan U.S. Aggregate Bond Index gained about 91 percent.

Bonds have beaten stocks for five-, 10- and 15-year periods. You have to start in 1993 to find a period in which stocks beat bonds up to the present day.

Cash, socked away in boring short-term Treasury bills, beat the S&P for the past 13 years.

Buying stocks is really a wager on the economy and corporate profits. With unemployment stuck at 9.6 percent and GDP growth slowing to a crawl, the U.S. economy might look like a sucker's bet.

That said, some see stocks as a roaring bargain today. Terril was a stock bear for most of the past decade, but he grew bull's horns after the crash of 2008.

"Now I keep buying stocks left and right because they're the cheapest asset category you can buy right now," says Terril.

He notes that stock prices are low compared to company profits. The S&P 500 is selling at 14 times trailing earnings and 13 times expected current-year earnings. That compares to a long-term historical average of 16.

The last long period of low PEs was in the 1970s, when interest rates and inflation were high. Investors could get a fat yield on bonds, so why would they buy stocks?

The opposite is true today, with interest rates teeny and inflation a no-show. Last week, a 10-year Treasury bond yielded 2.7 percent. That's a rate not seen for half a century. Corporate bonds with A3 investment-grade ratings and 10-year maturities were yielding 3.85.

In effect, corporate bond buyers were investing $26 for every $1 in annual interest on corporate bonds, and $37 per buck of interest on Treasuries. If you buy an S&P Index stock fund, you're paying $14 for every $1 in annual corporate earnings, and getting a 2 percent dividend to boot.

"Big blue-chip stocks have not been this cheap since the 1950s," says Terril. AT&T, for instance, is selling at 12 times earnings with a 6 percent dividend yield.

At Argent Capital Management in Clayton, senior analyst Scott Harrison is also a stock bull. Only twice in the last century have stocks performed so poorly for so long — during the Great Depression and in the stagflation 1970s.

Both set the stage for roaring bull markets, he notes.

Of course, stock prices are low for a reason — worry over a double-dip recession. Analysts have been busy ratcheting down profit estimates as the economic news got gloomier over the past few months.

Niemann expects a "very long slog" for the economy, which means sickly stock prices.

If you have a 10-year horizon, buying stocks now makes sense, she says. But if you want a profit in the next couple of years, better stick to bonds.

Stock bulls think the bond market is looking a bit like a bubble. The average multi-sector bond fund returned 15 percent over the past year, according to Morningstar.

But falling interest rates account for a lot of the recent performance. Bond prices rise when rates fall, and vice versa. So, some of today's bond investors may be chasing after returns that can't easily be repeated.

When the economy finally does pick up steam, we'll see higher interest rates and lower bond prices. That's OK if you own an individual bond and hold it to maturity; you'll get the face value of the bond. But bond funds never mature, and their share prices fall when rates rise.

For instance, Vanguard's Total Bond Market Index Fund would lose 4 percent of its share price if interest rates rise 1 percent. That would overwhelm the fund's 2.5 percent interest yield.

Will interest rates rise? Yes, eventually, says Scott Colbert, chief of fixed income investment at Commerce Trust in Clayton. But they won't rise soon and they might move lower in the meantime, he says.

The long rally in bonds is "not a bubble, but it could be very, very long in the tooth," says Colbert, who manages the $640 million Commerce Bond Fund.

Colbert notes that investors typically give short-shrift to bonds in their 401(k) investments. A move toward bonds reduces risk; bond funds may slump, but they don't crash the way stocks sometimes do.

"Bonds are your downside protection," he says.