比特币价格真的能涨到5万美元吗？

    去年12月初，随着比特币价格一路飙升，迅速突破1,200美元大关，社会对它的关注与日俱增。批评家们敲响了警钟，声称比特币价格已经出现泡沫。但包括金融记者菲利克斯•萨尔蒙在内的一些人意识到了加密货币的价值，认为比特币只是估价过高，就像2008年以前的房地产一样。

    其他人想得更远，他们认为比特币全是泡沫，几乎不存在固有价值，认为它更像是当年荷兰的郁金香效应，而不是房地产泡沫。持这种观点的人士包括诺贝尔奖得主罗伯特•席勒和美国联邦储配委员会的前任主席艾伦•格林斯潘。

    数字货币没有任何国家或现实世界商品的支持，遭遇这样的质疑也是情理之中的事情。但对比特币持乐观态度的人则认为，“支持”比特币的是它顺畅、廉价、采用分散化编程的支付系统的实用功能。今年1月在纽约州金融服务局（New York Department of Financial Services）举办的调查听证会上，数字货币公司Circle的首席执行官杰里米•奥莱尔就曾经说过：“比特币价值增长是因为人们把它作为支付平台的看跌期权。”

    一封在比特币观察人士和追随者中疯狂传播的匿名电子邮件展示了比特币几种假想的简单用途和它的投入使用之后的情形，以及比特币价格随后会出现的变化。如果亚马逊（Amazon）采用比特币作为所有商品的支付手段，那么将这家公司总价380亿美元的商品除以（撰写电子邮件时）约700万枚比特币的供应量，比特币的单价将会达到5,400美元。如果有3,000万美元的国际汇兑业务采用比特币来完成，光这一项就会使得比特币价格涨到4.2万美元。将这些再加上在线扑克游戏和加油站的交易量，比特币交易的总金额就会达到6,020亿美元，就算按照如今1,200万枚比特币的供应量计算，每个比特币也价值5万美元。

    斯坦福商学院（Stanford Graduate School of Business）的经济学教授苏珊•埃塞目前正在研究比特币，他表示：“这些数据是一个好的开端。从某种意义上说，就像是比特币价值的上限。”实际上，几乎没人认为比特币能在短期内应用于全部这些交易中，但总交易额与供应量的比率是理解比特币价格的起点——随着越来越多的消费者和机构选择使用比特币，总贸易额增长，比特币的价格就会水涨船高。

    埃塞根据这个基础公式，再加上各种变量，建立了一个分析框架。第一个变量是周转速度，也就是使用比特币进行消费的频繁程度。由于比特币与纸币不同，摩擦费用很低，因此，假如供应商或贸易商只是短期地持有比特币，同时把它与政府发行的货币进行双向兑换，比特币就可能拥有非常高的周转速度。埃塞表示，如此一来，用少量比特币就能实现大额的支付，比特币的价格就会维持在较低的水平。

    还有一些难以预测的高风险变量。显然，比特币未来的价格很大程度上依赖于人们对加密货币模式的接受程度。埃塞相信，分散化账目的加密货币模式是“比现有技术更为优越的真正简单而强大的技术”，一些重要因素会推动这类模式为人们所广泛接受。

    In the last year, and with increasing intensity following the early December price spike that briefly put Bitcoin above $1,200, critics have sounded the alarm that the price is a bubble. Some, like Felix Salmon, have recognized the value of the cryptocurrency, but argued that it is simply overvalued, much like pre-2008 real estate.

    Others haven't stopped there, claiming that bitcoin is all bubble, at the center of which is little or no intrinsic value -- something closer to a Dutch tulip mania than a real estate bubble. Those making the latter case have included Nobel Laureate Robert Shiller and former Federal Reserve Chairman Alan Greenspan.

    It seems reasonable enough to be skeptical of a digital currency unbacked by any state or real-world goods. But bitcoin optimists argue that what "backs" bitcoin is the functionality of its frictionless, low-cost, decentralized payments system. As Circle CEO Jeremy Allaire put it at fact-finding hearings held by the New York Department of Financial Services in January, "The growth in the value of bitcoin is a put option on its adoption as a payments platform."

    An anonymous viral e-mail circulating among bitcoin watchers and partisans lays out a few simple hypothetical usage and adoption scenarios, and their consequences for bitcoin's price. If Amazon.com (AMZN) adopted bitcoin for all payments, its volume of $38 billion, divided by a supply of (at the time of the email's writing) about 7 million bitcoin, would make each bitcoin worth $5,400. If $300 billion in international remittance was conducted in bitcoin, that volume alone would push the price to $42,000. Adding these, along with online poker and gas station transactions, would lead to a total transaction volume of $602 billion -- and a bitcoin, even at today's expanded supply of 12 million coins, worth $50,000.

    "Those numbers are good ones to start with. In some sense, that's like a maximum," says Susan Athey, a professor of economics at the Stanford Graduate School of Business who has been studying bitcoin. Few would realistically argue that bitcoin will service 100% of even these silos in the near term, but the volume/supply ratio is the starting point for understanding bitcoin price -- as more consumers or organizations choose to use bitcoin, increased volume will drive the price up.

    Building from that basic formula, Athey adds a variety of variables to build an analytic framework. The first is velocity -- how frequently a bitcoin can be spent. Because bitcoin, unlike paper money, is very low-friction, there's the possibility of a very high-velocity bitcoin, if, for example, vendors or traders only held bitcoin very briefly, cashing it in and out to government currencies on either end of transfers. That, Athey says, would allow a small volume of bitcoin to process a large volume of payments, keeping the price of bitcoin relatively low.

    Then there are even less predictable and higher-risk variables. Obviously, bitcoin's future price depends hugely on the adoption rate of the cryptocurrency model. Athey believes that the cryptocurrency model of distributed ledgers is "a really simple, powerful technology that is superior to existing technology," and there are major drivers that point toward wide adoption.