CHAPEL HILL, N.C. (MarketWatch) — At some point in the next five years, the U.S. stock market is likely to be more than 30% lower than where it stands today.

That is the frightening conclusion in a recent study by Swiss economic and financial consultancy Wellershoff & Partners. The company, whose chief executive is former UBS chief economist Klaus Wellershof, found a strikingly strong inverse correlation between the stock market’s valuation and its maximum drawdown over the subsequent five years.

The reason this finding is such bad news for U.S. stocks: As judged by the cyclically adjusted P/E (CAPE) ratio that is championed by recent Nobel laureate Robert Shiller, the U.S. stock market’s current valuation is at one of its highest levels in history. The latest CAPE reading is 25.69, which is 61% higher than its historical median of 15.95 (and 55% higher than the historical mean of 16.55).

Wellershoff & Partners found that, since 1900, the average five-year decline following CAPE levels as high as current readings is between 30% and 35%. In contrast, when the CAPE has been below 15, its average drop over five years was below 10%.

Furthermore, the study found that there is little basis in the historical record for thinking the market will somehow be able to sidestep a big decrease during the next five years: “Going back to 1900, there has been only one instance when the valuation levels we see today were not followed by drawdowns of 15% or more over the subsequent five to six years. Thus, at least for the U.S. market, it seems fair to say that the risk of losing capital is substantial.”

In addition, as you can see from the chart, there is a remarkable similarity in outcomes between developed and emerging markets. This increases our confidence that the inverse correlation the study reports is statistically significant.

To be sure, this recent study is not the first to point out the bearish implications of the above-average CAPE level in the U.S. But what is unique is that it focuses not on overall returns but on drawdowns. That’s important because long-term averages mask how volatile the market may be along the way, which, in turn, is related to how likely it is that we’ll bail out of stocks at some point in the next few years. The bailout point is usually at the point of maximum loss.

Imagine, for example, that the stock market will provide an inflation-adjusted return of 1% to 2% annualized over the next decade. That’s consistent with some analyses of what today’s high CAPE reading means. While that return is mediocre, it may still be high enough to convince you that it’s worth remaining invested in stocks, especially given the bleak outlook for long-term bonds.

But what if, on the way to producing that modest longer-term return, the market at some point plunges 35%? Many investors would find that loss intolerable and, therefore, bail out of stocks — which means they would not participate in any subsequent recovery that produces the net longer-term return of 1% to 2% annualized.

Note carefully that this study, by focusing on a drawdown that may occur at some point over the next five years, sheds no light on when it might occur. But if the study’s conclusions are right, the bulls are playing a very high-risk game.

Do you really want to play that game with your retirement assets?

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