Investing.com - Japan took a bold step in making bitcoin legal tender. Now it is taking thelead in trying to bring greater transparency to the industry by compiling domestic cryptocurrencytrading statistics.A joint study by the Financial Services Authority and the Japanese Cryptocurrency Business Association shows there are at least 3.5 million individuals in Japan trading cryptocurrencies. About 85% of that crypto trader population is between 20 and 50 years old. The largest group is investors in their 30s at 34%. Annual bitcoin trading soared from $22 million in 2014 to $97 billion in 2017.Trading using bitcoin as an underlying asset, such as futures, grew even more, jumping from $2 million in 2014 to $543 billion last year. The data is based on trading at Japan's 17 authorized exchanges.