Before revision:  The empirical results show that (1) the degree of market efficiency varies with time in cryptocurrency markets, (2) the market efficiency level of Bitcoin is higher than that of the other markets over most periods, and (3) the market efficiency of cryptocurrencies has evolved .
After revision:  The empirical results show that (1) the degree of market efficiency varies with time in cryptocurrency markets, (2) the degree of market efficiency varies with time, (2) Bitcoin's market efficiency level is higher than that of the other markets over most periods, and (3) the market efficiency of cryptocurrencies has evolved .