ExchangesAs of December 12 around 90 of all the bitcoin that will ever exist is in circulation today and the top five exchanges hold 16 million bitcoin The bitcoin holdings on Coinbase Binance Huobi Kraken and Okex combined represent 796 of the 21 million bitcoin supply cap The bitcoin held by Coinbase is a whopping 51 of the 16 million bitcoin or 416 billion using todays exchange rates