That question got a lot tougher in the past 12 months for pension fund managers around the country, who for the past decade and a half have been funneling cash to Dalio and his firm, which now manages $142 billion – making it the largest hedge fund in the U.S.

That’s because Dalio had a lousy 2012. By some reports, he was down for most of the year. Blog ZeroHedge appears to have a copy of Bridgewater’s most recent client letter, which details how it did in 2012. Dalio’s flagship hedge fund, Pure Alpha, ended the year up just 0.8%. That was much worse than the market in 2012. Stocks, as measured by the S&P 500, were up 13%. Bonds were up just over 4%. Even the average mutual fund manager, who gets paid far less than Dalio, was up 0.9% in the fourth quarter alone, just slightly better than Bridgewater did all year. For the full year, stock mutual fund managers were up 14%, handily beating Dalio.

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Of course, every investor has off years. And Dalio is certainly entitled to one. Even with last year’s flub, he still has one of the best track records of any investor. Pure Alpha has been up an average of 14% a year since 1991. Fortune, back in 2009, was one of the first major publications to profile Dalio and his success. So you could almost shrug off the $2 billion for an off year, I guess. (In good years, Dalio’s company gets much, much more. In 2011, when his flagship fund was up 20%, his firm took in around $6 billion in fees.)

But a close look at Dalio suggests 2012 could be more than an anomaly.

Dalio generally believes most people get diversification wrong. They hold 60% of their portfolio in stocks and the rest in bonds, or some similar split, and call it a day. Dalio says stocks have historically been far riskier than bonds, so if you truly want to diversify your portfolio you have to put far more money in bonds than stocks.

According to the Wall Street Journal, Dalio preaches what he calls risk parity to institutional investors around the country, and has gotten a number of large pension funds to lever up their portfolios and buy more bonds. And they’re doing this at a time when everyone appears to be growing more and more worried that the bond market could be in a bubble.

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That sounds scary, but that’s not the real problem. Dalio is, after all, about diversification. And he has recently joined the chorus of people who are warning that the bond market is overvalued.

If bonds do drop, Dalio’s bets on stocks in theory should balance that out. The real problem is bonds are no longer the safe bet they once were. Rick Rieder, who is chief investment office of fundamental fixed income portfolios at Blackrock (BLK), says 30-year bonds were actually more volatile than stocks last year.

So Dalio’s real bet — that bonds are less risky than stocks — is what was really off in 2012, and with interest rates at all-time lows that looks likely to continue for some time.

This is a simplistic analysis. Dalio only really practices risk parity with a little less than half of the money he manages. It’s called the All Weather fund, which actually did better than Pure Alpha in 2012. Pure Alpha, on the other hand, as you can see from the numbers from ZeroHedge makes dozens of bets on all types of investments. But here too you can see the shift. Among the biggest movers in its portfolio recently are investments in US and European bonds. Its stock market investments, by comparison, have been less volatile.

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Most people believe Dalio’s success was built on his great macro calls, a swashbuckler able to stay one step ahead of the global economy. But while Pure Alpha is not the fully diversified All Weather, its outsized returns have been driven by the same general Dalio investment thesis: That investors have traditionally taken on too much stock market risk, and need to spread their bets.

That’s been the true key to Dalio’s success. And during a time of falling interest rates, it has worked great. And it may continue to. But it’s also just the type of talk – that something like levering up your portfolio is safe as long as you use that leverage to buy bonds – that always pops up, and gets taken as gospel, just as bubbles are about to burst.