SINCE the heady days of late 2017 and January of this year, crypto-currencies have gone into retreat. Bitcoin, the best-known example, is now worth just a third of its value at its peak (see chart).

经过了2017年末和今年1月的风光，加密货币进入衰退期。作为加密货币的代表，比特币价值只有其最高价值的三分之一（见图表）。

But there remain plenty of true believers in digital currencies. They point out that prices are still well above where they were in 2016. And interest from institutional investors is still strong enough for analysts to want to make sense of the crypto-phenomenon.

但现在仍然有很多数字货币的真正信徒。他们指出，数字货币现在的价格仍远高于2016年的水平。同时， 机构投资者仍有着浓厚的兴趣，这足以让分析师想要了解这一加密现象。

The latest bank to take a shot is Barclays, which devotes a lot more of its “Equity Gilt Study 2018” to the impact of technological change on finance and the economy than it does to either equities or gilts. Its report describes crypto-technology as “a solution still seeking a problem”.

最新入局数字货币的是巴克莱银行。该行在《2018年度股票债券投资研究年度报告》中用了大篇幅内容讲述金融和经济方面的技术变革所带来的影响，而非仅仅是对股票或债券投资的影响。这份报告将加密技术称为“仍在寻求问题的解决方案”。

It identifies four challenges in particular. The first is trust. In most countries, consumers and businesses have faith in the currencies issued by the government. The second is sovereignty: the potential for tax avoidance and loss of financial control means that neither governments nor central banks will be keen to see private crypto-currencies take off.

它特别确定了四项挑战。第一个挑战是信任。在大多数国家，消费者和企业都相信政府发行的货币。第二个挑战是主权：避税和失去金融控制的可能性意味着政府和中央银行都不愿意看到私人加密数字货币的发展。

A third challenge is privacy. Although they can be used pseudonymously, crypto-currencies are less reliably anonymous than cash since the blockchain that lies behind them records all transactions. If a pseudonym is cracked, the user’s purchase history is revealed. A fourth relates to the ability to undo a transaction in cases of error or fraud—blockchain transactions are hard to reverse.

第三个挑战是隐私。尽管用户可以匿名使用，但加密货币背后的区块链记录了所有交易，它的匿名程度不如现金可靠。如果假名被破解，用户的购买记录就会曝光。第四个挑战是在出现错误或欺诈的情况下撤销交易的能力 - 区块链交易难以回撤。

On top of all these problems is the fact that existing alternatives seem to work perfectly well. It is easy to make payments and transfer money in an instant.

除了所有这些问题之外，现有的替代方案看起来非常奏效。即时付款和转账非常容易。

So what is the appeal of digital newcomers? Private crypto-currencies can be attractive in societies where trust is low, or where governments are unwilling or unable to provide reliable means of exchange—in wartime or during periods of sovereign default, for example. Barclays also suggests that in countries where opportunities to invest are limited, “crypto-currencies may be one of the few ways to diversify savings out of domestic assets.”

那么数字货币的吸引力是什么呢？例如，在信任度较低的社会，或者政府不愿或无法提供可靠的交换手段的情况下（如在战时或主权债务违约期间），私人加密数字货币可能具有吸引力。巴克莱银行还建议，在投资机会有限的国家，“加密数字货币可能使储蓄多样化，将其从国内资产中分散出来的少数方式之一”。

None of these conditions applies in rich countries. But they hold in some emerging markets. There could also be demand in the developed world from criminals (although they now strongly favour cash). By making generous assumptions about the size of these low-trust and criminal markets, Barclays comes up with a maximum total value for all crypto-currencies of $660bn-780bn. That is roughly where they were priced at the beginning of 2018.

这些条件在发达国家都不适用。但在有一些新兴市场，他们很适用。发达国家的犯罪分子可能有需求（虽然他们现在强烈偏爱现金）。通过粗略估计这些信任度低的犯罪市场的规模，巴克莱银行推算加密数字货币的最大总值达到6,000亿美元至7,800亿美元。这是参考了2018年初的比特币价格。

Maximum value is not the same as fair value. Surveys indicate that most people who buy bitcoin are doing so as an investment. Just 8% of Americans who hold bitcoin do so for purchases or payments. That suggests the main motive for buying crypto-currencies is speculation, which also explains their spectacular recent rise and fall, as with so many bubbles before them, from tulips to dotcom stocks.

最大值与公允价值不同。调查表明，大多数购买比特币的人是出于投资的目的。只有8％的持有比特币的美国人是为了购买或支付。这意味着购买加密数字货币的主要动机是做投机买卖，这也解释了他们近期大幅涨跌的情况，就像他们之前如此多的泡沫一样，从“郁金香现象”到网络股。

Speculative bubbles are hard to model—how to find a rational way to assess irrationality? But Barclays uses the ingenious parallel of an infectious disease. A bubble starts with a small number of asset owners (the “infected”). New buyers are drawn in (or catch the bug) because they witness price increases and fear they will miss out. A large share of the population is immune and will never succumb.

投机泡沫很难变成模式——如何找到一种理性方法评估非理性行为？巴克莱使用了“传染病”的巧妙类比。泡沫始于少数资产所有者（“受感染者”）。新买家被哄骗（或着迷），因为他们见证了价格上涨，他们害怕会错过。但大部分人对此是免疫的，永远不会“死亡”。

Buyers use a combination of the current price and an extrapolation of the recent increase in price to estimate their expected target value. The faster the price rises, the wilder investors’ hopes and the more the infection spreads. Eventually the market runs out of potential participants and the price rise slows. Once it starts to fall, holders lose hope of big gains and start to sell. The epidemic dies out.

买家使用当前价格和近期价格上涨的外推法的组合来估计其预期目标价值。价格上涨的速度越快，投资者的希望越大，感染蔓延越多。最终市场上的潜在参与者已经耗尽，价格上涨放缓。一旦开始下跌，持有者就会失去大收益的希望并开始出售。流行病消失了。

The Barclays model fits the history of the bitcoin price pretty well. And it suggests that the long-term outlook for the value of crypto-currencies is bleak. After all, plenty of people will have bought in the past few months, when enthusiasm was at its height. Some will have taken extra risk to buy the currency, via spread betting or other types of gambling. Instead of the riches they expected, they will be nursing losses. Some will be keen to sell their holdings. But new buyers will be harder to tempt now that crypto-currencies no longer look like a one-way bet.

巴克莱的这种模型非常适合用来描述比特币价格的历史。这个模型认为，加密数字货币的价值前景暗淡。毕竟，在过去的几个月里，很多人都会在热情高涨的时候买进。有些人因为打赌或其他类型的赌博愿意冒额外的风险购入这种货币。除了他们预期的收益，他们还可能会蒙受损失。有些人会热衷于出售他们的股份。但既然现在加密数字货币不再看起来像单向投机，新买家也不容易上当。

All of this is good news. Perhaps the blockchain will turn out to be useful for other purposes—for example, recording property transactions. But it has been hard to think about such potential innovations when all the attention was focused on an ever-rising price. The crypto-fever has finally broken.

所有这些都算是好消息。也许区块链会另有他用，如记录财产交易。但是，当所有的注意力集中在不断上涨的价格时，很难想到这种潜在的变革。对加密的狂热终于归于尘土。

编译：王梦颖

编辑：翻吧君

来源：经济学人（2018.04.14）