????眼下，和我們認為是“常態”的長期趨勢相比，這么多影響股價的指標都處于如此偏離的狀態，這種情況很少見。公司盈利遠高于歷史正常水平，利率在美聯儲（Fed）的干預之下遠低于正常值，會隨著債券收益率下降而上漲的債券價格似乎也處在不正常的高點上。普通投資者也許會想到，面對這樣的情況，棒球明星約吉?貝拉可能會說：“‘新的常態’這么不正常，讓我感到困惑。”

????由于如此之多的影響因素都處于如此不尋常的水平，投資者很難判斷股票是真的便宜，或者至少定價合理，還是極為昂貴。華爾街的內行們一般都會說股票很廉價，而且會催促大家更多地買進；與此同時，通常具有預見作用的量化基準指標都會表明，股票的估值已經特別高，因而要小心謹慎。到底應該相信誰呢？

????為了消除這種困惑，我們不妨來比較一下股票在兩種情形下可能實現的未來回報率。在第一種情形中，我們假設當前指標將保持不變，這樣“新的常態”將在今后幾年延續下去。在第二種情形中，我們假設50年來在大部分時間里都很流行的指標將再次成為主導。第二種情況也就是所謂的“均值回歸”，是指市場各項指標向歷史正常水平靠攏的趨勢，牽動它們的則是類似于重力的經濟力量。

????要搭建這樣的框架，要點就在于估算盈利、分紅、股價和未來回報率的決定因素目前都處于什么樣的水平。然后，我們將按照上面這兩種情形考察一下它們在今后10年中的可能動向。CAPE，或者說經過周期性調整的市盈率，是個絕佳的切入點。建立這項指標的是2013年諾貝爾經濟學獎得主、耶魯（Yale）大學教授席勒。他采用的不是當前利潤，而是剔除了通脹因素的10年平均每股收益。這個項數據熨平了一直起伏不定的高點和低點——而現在，我們正處于歷史高點。席勒用標普（S&P）指數目前的平均股價除以這個10年平均每股收益后得到了CAPE。

????為什么要相信CAPE？來自投資策略機構Research Affiliates的羅勃?阿諾特和投資管理公司AQR Capital的克里夫?阿斯尼斯都是投資領域最聰明的人之一。和席勒一樣，他們也認為CAPE是衡量股票貴賤的最佳指標，或者最佳指標之一，也是預測未來回報率的優秀向導。簡單地說，CAPE越低，今后10年的收益就越高，預期就是這樣。

????目前CAPE為25.4倍。和幾乎所有市場指標一樣，現在的CAPE遠高于正常水平。過去20年中，CAPE平均為18倍左右，100年來的平均CAPE還要更低一些。

????按照上述第一種情形，或者說“現在即將來”的假設，我們預計今后10年CAPE將保持現有水平。也就是說，剔除通脹因素后，投資者獲得的回報率相當于1除以CAPE，或者說他們的“盈利收益率”為3.93%，就算是4%吧（如果一只股票的市盈率或者CAPE是25倍，它的盈利回報率就一定是4%）。

????此時的總回報率就是4%加上2%左右的通脹率，即6%。它來自兩個方面。第一個是每年約1.6%的股息收益率（目前大公司將40%的利潤用于分紅），第二個是每股收益每年增長4.4%。要知道，每股收益的增長速度遠低于公司的整體盈利水平——長期來看，公司整體盈利都隨著GDP波動。出現這種情況的原因是，一般來說公司每年都會發行大量新股，規模會超過它們回購的股票，目的是為擴張計劃提供資金。

????這很難稱得上是一種美妙的展望，而且和華爾街預計的富裕未來相比，它也有很長的一段路要走。然而，第二種情況要讓人氣餒得多，從中可以看出均值回歸所隱藏的卑鄙之處。

????Seldom have so many of the metrics that influence stock prices strayed so far from the long-term trends we've come to consider "normal." Corporate earnings are far above what's normal historically, interest rates are way below normal because of Fed intervention, and bond prices that wax when rates wane are hovering at seemingly unnatural heights. The typical investor might echo something Yogi Berra could have said: "I'm confused by the 'new normal' because it's so unusual."

????Because so many influential factors are so unusual, investors struggle to determine if stocks are really cheap or at least reasonably priced, or extremely expensive. Wall Street mavens generally argue that equities are a bargain, and urge you to buy more, while usually prescient, quantitative benchmarks show extra-rich valuations, and urge caution. What to believe?

????To clear the confusion, let's compare the likely future equity returns from two scenarios. In the first, we assume that the current metrics will remain in place, so that the "new normal" persists for years to come. In the second, we predict that the metrics that have prevailed during most of the past half-century return in force. That's called "mean reversion," the tendency for market rates and ratios to go back to their historic norms, tugged by a kind of gravitational economic force.

????To set the framework, it's important to gauge where earnings, dividends, and prices, the determinants of future returns, sit right now. Then we'll examine where they're likely to go in 10 years under the two sets of assumptions. An excellent starting point is the CAPE, or cyclically adjusted price-earnings ratio, developed by 2013 Nobel laureate Robert Shiller of Yale. Instead of using current profits, a highly erratic measure, Shiller employs a 10-year average of inflation-adjusted earnings per share that smoothes the constantly-shifting peaks and valleys -- right now we're at a historic peak. He divides that adjusted earnings number into the current S&P average to arrive at the CAPE.

????Why trust the CAPE? Two of the best minds investing, Rob Arnott of Research Affiliates and Cliff Asness of AQR Capital agree with Shiller that it's either the best, or one of the best, measures of whether stocks are cheap or dear, and an excellent guide to future returns. Put simply, the lower the CAPE, the better the gains in the decade to come, WI.

????Today, the CAPE stands at 25.4. Like almost every market metric out there, the current CAPE is way out of the ordinary -- on the high side. The average CAPE over the last two decades is around 18, and for the past century, a couple of points lower.

????For our first, "now is our future" assumption, we'll project that the CAPE stays at its current level for the next decade. That means investors will get an inflation-adjusted return equal to the inverse of the CAPE, or the "earnings yield," of 3.93%, let's call it 4%. (If a company's PE or CAPE is 25, its earnings yield must be 4%.)

????The total expected return is that 4% plus inflation of around 2%, or a total of 6%. That return comes in two parts. The first is the dividend yield of around 1.6% a year (large companies today pay out about 40% of their profits), and the second is earnings-per-share growth of 4.4% annually. Keep in mind that earnings per share increase at a far slower rate than overall corporate earnings that over long periods track GDP, because companies typically issue large numbers of shares each year, in excess of buybacks, to fund their plans for expansion.

????That's hardly a wonderful outlook, and it's a long way from bountiful future Wall Street expects. But the second scenario is far more daunting. It demonstrates the dastardly meanness in mean reversion.