Using modern terminology, money always evolves in the following four stages:
Collectible: In the very first stage of its evolution, money will be demanded solely based on its peculiar properties, usually becoming a whimsy of its possessor. Shells, beads and gold were all collectibles before later transitioning to the more familiar roles of money.
Store of value: Once it is demanded by enough people for its peculiarities, money will be recognized as a means of keeping and storing value over time. As a good becomes more widely recognized as a suitable store of value, its purchasing power will rise as more people demand it for this purpose. The purchasing power of a store of value will eventually plateau when it is widely held and the influx of new people desiring it as a store of value dwindles.
Medium of exchange: When money is fully established as a store of value, its purchasing power will stabilize. Having stabilized in purchasing power, the opportunity cost of using money to complete trades will diminish to a level where it is suitable for use as a medium of exchange. In the earliest days of Bitcoin, many people did not appreciate the huge opportunity cost of using bitcoins as a medium of exchange, rather than as an incipient store of value. The famous story of a man trading 10,000 bitcoins (worth approximately $94 million at the time of this article’s writing) for two pizzas illustrates this confusion.
Unit of account: When money is widely used as a medium of exchange, goods will be priced in terms of it. I.e., the exchange ratio against money will be available for most goods. It is a common misconception that bitcoin prices are available for many goods today. For example, while a cup of coffee might be available for purchase using bitcoins, the price listed is not a true bitcoin price; rather it is the dollar price desired by the merchant translated into bitcoin terms at the current USD/BTC market exchange rate. If the price of bitcoin were to drop in dollar terms, the number of bitcoins requested by the merchant would increase commensurately. Only when merchants are willing to accept bitcoins for payment without regard to the bitcoin exchange rate against fiat currencies can we truly think of Bitcoin as having become a unit of account.
Monetary goods that are not yet a unit of account may be thought of as being “partly monetized”. Today gold fills such a role, being a store of value but having been stripped of its medium of exchange and unit of account roles by government intervention. It is also possible that one good fills the medium of exchange role of money while another good fills the other roles. This is typically true in countries with dysfunctional states, such as Argentina or Zimbabwe. In his book Digital Gold, Nathaniel Popper writes:
In America, the dollar seamlessly serves the three functions of money: providing a medium of exchange, a unit for measuring the cost of goods, and an asset where value can be stored. In Argentina, on the other hand, while the peso was used as a medium of exchange — for daily purchases — no one used it as a store of value. Keeping savings in the peso was equivalent to throwing away money. So people exchanged any pesos they wanted to save for dollars, which kept their value better than the peso. Because the peso was so volatile, people usually remembered prices in dollars, which provided a more reliable unit of measure over time.
Bitcoin is currently transitioning from the first stage of monetization to the second stage. It will likely be several years before Bitcoin transitions from being an incipient store of value to being a true medium of exchange, and the path it takes to get there is still fraught with risk and uncertainty. It is striking to note that the same transition took many centuries for gold. No one alive has seen the real-time monetization of a good (as is taking place with Bitcoin), so there is precious little experience regarding the path this monetization will take.
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