Bitcoin is a digital asset invented by Satoshi Nakamoto that was designed to work in peer-to-peer transactions as a currency.[5][126] Bitcoin does not work easily in transactions, or as a currency.[127][29] Bitcoins have three qualities useful in a currency, according to The Economist in January 2015: they are "hard to earn, limited in supply and easy to verify".[128] Economists define money as a store of value, a medium of exchange, and a unit of account and agree that bitcoin does not meet all these criteria.[129] As of March 2014, the bitcoin market suffered from volatility, limiting the ability of bitcoin to act as a stable store of value, and retailers accepting bitcoin use other currencies as their principal unit of account.[129]
Liquidity (estimated, USD/year, logarithmic scale).[68]
According to research by Cambridge University, between 2.9 million and 5.8 million unique users used a cryptocurrency wallet in 2017, most of them for bitcoin. The number of users has grown significantly since 2013, when there were 300,000 to 1.3 million users.[12]
