????第二類投資指的是永遠也不會有產出的資產，投資者買入時只是希望其他投資者——這些人同樣也明白這類資產永遠都不會有產出——將來會以更高的價格接手。最典型的就是郁金香，17世紀時，它一度成為此類買家的最愛。

????這類投資需要買家群體不斷壯大，而人們之所以決定買入，是因為他們相信未來買家群體還會繼續壯大。這類資產的持有者并不指望資產本身能有什么產出——它永遠都不會有產出——而是相信未來，別人會更迫切地希望接手。

????這類資產中的一個大類就是黃金，它當前極受避險投資者的追捧。這些投資者對其他幾乎所有資產都不放心，特別是紙幣（正如前述，鑒于紙幣的購買力，他們的擔心不無道理）。不過，黃金有兩個顯著的缺點。它用途有限，也不能自我繁殖。的確，黃金有一些工業和裝飾用途，但這些用途的需求有限，不足以消化新的產量。而且，如果某個投資者一直持有一盎司黃金，最終依然還是只持有一盎司黃金。

????大多數投資者買入黃金是因為他們相信上述擔心會升級。過去十年證明這一信念是正確的。此后，金價的繼續走高是源于這波走勢激發的、更旺盛的購買熱情，很多人都將金價上漲視為這種投資觀點得到了驗證。隨著“跟風”投資者的涌入，他們短期內會建立起自己的真理。

????起初合理的投資邏輯加上反復炒作的價格上漲便能造就巨大的資產泡沫，過去15年里我們看到的互聯網泡沫和樓市泡沫便是典型。在這些泡沫中，很多最初持懷疑態度的投資者最終都向市場給出的“證據”低了頭，一時之間買家群體飛速擴張，足以維持泡沫的繼續膨脹。但泡沫大到一定程度，總是免不了會破滅。真是應了那句老話：“聰明人起頭，傻瓜結尾”（What the wise man does in the beginning, the fool does in the end）。

????今天，全球的黃金庫存有約17萬公噸。所有這些黃金熔合在一起會形成一個邊長68英尺的立方體。（想象一下，差不多正好能夠放入一個棒球場內場。）以每盎司1,750美元（此文撰寫時的金價）計算，它的市值約為9.6萬億美元。我們將這個立方體稱為A組。

????現在，我們用同樣金額創建一個B組。我們可以買下美國所有的耕地（4億英畝，年產值約2,000億美元）和16家?？松梨冢‥xxon Mobils）（全球最賺錢的公司，每年利潤額超過400億美元）。然后，還剩下約1萬億美元可用作活動資金（因此，就算這樣大手筆的投資后，也絲毫不會感到手頭緊張）。你認為一個擁有9.6萬億美元的投資者會選擇A組，還是B組？

????除了庫存黃金的驚人市值，當前居高不下的金價也讓如今的黃金年產值達到了約1,600億美元。買家——不管是珠寶制造商、工業用戶，心存恐懼的個人，還是投機者——必須不斷地消化增加的供應，才能讓金價繼續在當前水平保持均衡。

????The second major category of investments involves assets that will never produce anything, but that are purchased in the buyer's hope that someone else -- who also knows that the assets will be forever unproductive -- will pay more for them in the future. Tulips, of all things, briefly became a favorite of such buyers in the 17th century.

????This type of investment requires an expanding pool of buyers, who, in turn, are enticed because they believe the buying pool will expand still further. Owners are not inspired by what the asset itself can produce -- it will remain lifeless forever -- but rather by the belief that others will desire it even more avidly in the future.

????The major asset in this category is gold, currently a huge favorite of investors who fear almost all other assets, especially paper money (of whose value, as noted, they are right to be fearful). Gold, however, has two significant shortcomings, being neither of much use nor procreative. True, gold has some industrial and decorative utility, but the demand for these purposes is both limited and incapable of soaking up new production. Meanwhile, if you own one ounce of gold for an eternity, you will still own one ounce at its end.

????What motivates most gold purchasers is their belief that the ranks of the fearful will grow. During the past decade that belief has proved correct. Beyond that, the rising price has on its own generated additional buying enthusiasm, attracting purchasers who see the rise as validating an investment thesis. As "bandwagon" investors join any party, they create their own truth -- for a while.

????Over the past 15 years, both Internet stocks and houses have demonstrated the extraordinary excesses that can be created by combining an initially sensible thesis with well-publicized rising prices. In these bubbles, an army of originally skeptical investors succumbed to the "proof " delivered by the market, and the pool of buyers -- for a time -- expanded sufficiently to keep the bandwagon rolling. But bubbles blown large enough inevitably pop. And then the old proverb is confirmed once again: "What the wise man does in the beginning, the fool does in the end."

????Today the world's gold stock is about 170,000 metric tons. If all of this gold were melded together, it would form a cube of about 68 feet per side. (Picture it fitting comfortably within a baseball infield.) At $1,750 per ounce -- gold's price as I write this -- its value would be about $9.6 trillion. Call this cube pile A.

????Let's now create a pile B costing an equal amount. For that, we could buy all U.S. cropland (400 million acres with output of about $200 billion annually), plus 16 Exxon Mobils (the world's most profitable company, one earning more than $40 billion annually). After these purchases, we would have about $1 trillion left over for walking-around money (no sense feeling strapped after this buying binge). Can you imagine an investor with $9.6 trillion selecting pile A over pile B?

????Beyond the staggering valuation given the existing stock of gold, current prices make today's annual production of gold command about $160 billion. Buyers -- whether jewelry and industrial users, frightened individuals, or speculators -- must continually absorb this additional supply to merely maintain an equilibrium at present prices.