股市再創新高，對那些已經持倉的股民而言自是再好不過。不過股票直線上漲也有不利之處。手握現金，尋求低價買入的投資者此時只能繼續觀望。面對日益高企的股價，那些想把儲蓄資金投入股市的人不得不按兵不動。

高歌猛進的股價也給長期投資者設下了困局，因為如今股價處于高位，將來再有大幅增長的可能性已經不高。過去十年里，標普500指數中經過通貨膨脹調整后的平均股票價格已經達到了每股盈利的約30倍（也就是所謂的周期調整市盈率）。歷史上看，在這個水準的市盈率之后，往往緊接著令人失望的低回報期。

這就是為何投資者在股市慘淡之際購買股票會感到更加放心。好消息是，即使在股市整體上揚的情況下，也總有一些熊市存在。在逢低買入的投資者眼里，有三類資產并未被這輪牛市所帶動，如今顯得尤為特立獨行。

New highs in the stock markets are great for those who already own stocks. But there is a downside when stocks seemingly do nothing but rise. Any investor who’s been holding cash, waiting for lower prices and a better entry point, has had to keep waiting. And those deploying new savings into the markets have had to do so at higher and higher prices.

Those rising prices are also a catch-22 for long-term investors, because pricey markets today make impressive future gains less likely. The S&P 500 currently trades at about 30 times its average inflation-adjusted earnings over the past 10 years (the so-called CAPE ratio). Historically, levels anywhere near that high have almost always preceded periods of disappointing returns.

That’s why many investors are more comfortable buying shares when there’s blood in the streets. And the good news for those investors is that there will always be a bear market somewhere, even when the broad market is killing it. Three asset classes that have been left behind during this bull run stand out in particular right now in the eyes of bargain hunters:

能源股

石油價格在2008年6月達到每桶150美元的巔峰。從那以后，水力壓裂法的革命帶來了新的產出，再加上低通貨膨脹，石油價格從那以后已經下跌了三分之二，能源公司的利潤也受到沉痛打擊。2008年中期至今，能源股一直是標普500指數中表現最差的類型，甚至和倒數第二都相距甚遠：基金The Energy Select Sector SPDR ETF（XLE）的跌幅超過13%，而同期標普500指數整體卻有超過200%的漲幅。僅有的安慰獎是高股息：例如，基金The Energy Select Sector SPDR ETF目前的股息為3.8%，是整體市場平均水平的兩倍有余。

貴金屬和礦業股

這些商品生產者的股票往往表現出很大的波動性，因為它們對經濟增長和商品本身不確定的供需情況高度敏感。共同基金Vanguard Global Capital Cycles（VGPMX）很好地體現了金屬市場和相關商品市場的情況，它在這段時間里連跟上市場的腳步都做不到：過去十年里，該基金跌幅近50%。（相對平庸的全球經濟增長又一次成為元兇。）投資者青睞貴金屬和礦業股，往往因為它們與整體市場走勢關聯不大，可以讓投資組合變得更加多樣化。不過，持有不相關的資產經常也意味著投資者會在市場其他股票突飛猛進時吞下重大損失。

價值股

互聯網泡沫破滅后，價值股——那些與對應企業的價值相比估值過低的股票——漲幅大大超過增長股。不過金融危機以來，在亞馬遜（Amazon）、Netflix、谷歌（Google）和Facebook等在投資者面前占盡風光的公司的帶領下，增長股把價值股遠遠甩在了身后。科技創新、尤其是軟件創新對經濟的影響力日益加大，專利、版權、商標等無形資產價值不斷提高，投資者也有了在資本世界額外付費的意愿，這一切共同推動著股價大步邁進。

然而，投資者認為拐點將近。投資巨頭AQR Capital Management的掌門人克利夫·阿斯尼斯在最近一篇文章中通過一系列指標指出，增長股的價格達到了互聯網泡沫以來的新高。他寫道，與之相反：“除去技術泡沫，價值股的價值則是這一時段的最低水平。”

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當然，某股很便宜，不代表它不會變得更便宜。正如我們的例證所示，這幾類股票表現糟糕都是有原因的。這讓投資者對目前的狀況感到疑惑：你似乎只能選擇投資那些基礎良好卻價格較高的股票，或局勢惡化卻價格較低的股票。沒錯，歷史告訴我們，經濟的循環終究會開動起來，金屬股和價值股又將成為主角，但它不會告訴我們具體時間。

最好的做法可能是試圖放下對“具體時間”的擔憂。許多投資者（包括我的公司）傾向于選擇多樣化投資的長期策略。在實踐中，這往往意味著在遭遇最嚴重打擊的那塊市場中投入部分資金，從而利用低價進入的優勢。在決定是否買入受到重創的資產時，請牢記以下經驗：

沒有萬無一失的萬金油策略

價值投資經過專業學者、職業投資者和標志性的沃倫·巴非特的反復審視，被認為是一種長期有效的策略。不過即使合理的投資策略也注定會經歷表現不佳的痛苦期。畢竟，任何資產獲得超出通脹率的收益，唯一的原因在于持有它們具有風險——“合理”并不意味著“無風險”。

多樣化投資意味著你得一直說抱歉

多樣化投資的主要原因是避免把你的錢長期集中到表現糟糕的資產上。不過擴大投資面也意味著你的投資組合中至少會有一部分走向夭折，盡管其他的能夠蓬勃發展。你要接受偶爾的失敗，這樣才能增加獲勝的概率。

不要忘記調整資產分配

只有你定期重新調整資產分配，多樣化投資的策略才能起效。本質上，這意味著賣出部分表現出色的資產，并買入一些境況不佳的資產。上文中提到的所有類型的資產，在失寵之前都曾經有過投資回報率很高的時期。你之前有沒有在它們風光無限時減持股份，從而將它們的權重調整到目標水平？如果沒有，它們帶來的虧損會給你造成更大痛苦——也會讓你更難在此時作出買入的決定，盡管從戰略上看，你應該這么做了。（財富中文網）

本文作者本·卡爾森（Ben Carlson）是里薩茲財富管理公司（Ritholtz Wealth Management）機構資產管理部門的主任。他的公司在價值型股票基金中持有份額，但不是本文中提到的任何具體基金。

本文另一版本登載于《財富》雜志2020年1月刊，標題為《在牛市中購買“熊股”》。

譯者：嚴匡正

Energy stocks

Oil prices topped $150 a barrel in June 2008. Since then, new production unleashed by the fracking revolution, combined with low inflation, has helped drive oil prices down by two-thirds—while hammering energy-company profits. Energy has been by far the worst-performing sector of the S&P 500 since mid-2008, and it’s not even close: The Energy Select Sector SPDR ETF (XLE) has fallen more than 13%, versus a gain of more than 200% for the S&P 500. One consolation prize is high dividends: XLE, for example, currently yields 3.8%, more than twice what the broader market yields.

Precious metals and mining stocks

These commodity-producer stocks often exhibit wild volatility because they’re unusually sensitive to economic growth and fluctuating supply and demand for the commodities themselves. Vanguard Global Capital Cycles (VGPMX), a mutual fund that’s a good proxy for the metals markets and related commodities, has done worse than just trail the market during this cycle: Over the past 10 years, the fund is down nearly 50%. (Again, relatively modest global growth is a culprit.) Investors often seek metals and mining stocks because they have a low correlation to the broader market, offering the benefits of a diversified portfolio. But sometimes owning uncorrelated assets means eating big losses while the rest of the market screams higher.

Value stocks

After the dotcom bubble deflated, value stocks—stocks that are cheap relative to the value of their underlying businesses—went on a run of huge outperformance over growth stocks. But growth has beaten the pants off value since the financial crisis (see graphic), led by high-growth companies such as Amazon, Netflix, Google, and Facebook that have monopolized investor mindshare. The growing economic impact of tech innovation, particularly in software; the rising value of intangible assets like patents, copyrights, and trademarks; and the willingness of investors to pay extra for growth in a world awash in capital have all contributed to growth’s edge.

Still, investors think a turning point could be near. Using a number of metrics, Cliff ?Asness, head of investment giant AQR Capital Management, showed in a recent piece that growth stocks are more expensive now than at any time other than the dotcom bubble. In contrast, Asness writes, “Excluding the tech bubble, the value of value is the cheapest it’s ever been.”

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Of course, just because something is cheap doesn’t mean it can’t get cheaper. As our examples show, each of these categories has a black eye for a reason. That’s what makes the current situation for investors so confusing: It can seem like your only choices are to invest in assets with good fundamentals but high prices or to invest in assets with deteriorating fundamentals but low prices. Yes, history tells us that economic cycles will eventually boost energy and metals stocks and value stocks again, but it won’t tell us when.

The best move may be to worry less about “when.” Many investors (including my firm) favor a long-term strategy that involves broad diversification. In practice, that often means investing some capital in the areas of the market that have been hit the hardest, to take advantage of the cheap entry point. When deciding whether to wade into beaten-down asset classes, here are some lessons to keep in mind:

Nothing works all the time

Value investing has been repeatedly vetted by academics, professional investors, and the iconic Warren Buffett as an approach that works over the long term. But even sound investment strategies are bound to go through painful periods of underperformance. After all, the only reason any assets earn a premium over the rate of inflation is because owning them involves risks—and “sound” doesn’t mean “risk-free.”

Diversification means always having to say you’re sorry

The main reason to diversify is to avoid concentrating your money in a terrible-performing asset for an extended period. But spreading your bets also means that at least part of your portfolio will be sucking wind while the rest of it sprints ahead. You’re accepting the occasional strikeout to increase your odds of winning the game.

Don’t forget to rebalance

Diversification works only if you periodically rebalance your asset allocations. In essence, this means selling a little bit of what has done well to buy a little bit of what hasn’t. All of the asset classes above experienced strong returns before their fall from grace. Did you sell off a bit during the good times to bring them back to their target weights? If not, their losses have been even more painful for you—which could make it even harder to buy now, when strategy might dictate that you should.?

Ben Carlson is director of institutional asset management at Ritholtz Wealth Management. His firm has positions in value stock funds, but not in any specific fund mentioned here.

A version of this article appears in the January 2020 issue of Fortune with the headline “Buying ‘Bears’ in a Bull Market.”