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Since its origins, Bitcoin has maintained a central role in the crypto market. Bitcoin's dominance — that is, the proportion of Bitcoin's market capitalization relative to the total cryptocurrency market — has shown dramatic fluctuations.
In the early years (2013–2016), Bitcoin dominated almost the entire ecosystem, with an average daily dominance between 82% and 93%; it reached an all-time high of 99.1% on May 29, 2013. With the arrival of Ethereum in 2015 and the ICO boom in 2017, that supremacy began to wane. By mid-2017, dominance fell below 50% for the first time (48.5%) and hit an all-time low of 31.1% in January 2018.