Until the end of 2013, Bitcoin was predominantly traded for US dollars. However, after the crash of 2013, miners consolidated in China and Bitcoin mostly traded for Chinese yuan[1]. At the start of 2017, regulators in China cracked down on digital currency exchanges[2] and trading quickly moved to Japanese yen and, more recently, South Korean won[3].
All of the early buyers are selling. This won't end well.
[1]: http://www.businessinsider.com/bitcoin-trading-china-yuan-re...
[2]: http://fortune.com/2017/01/05/bitcoin-plunge-china-currency/
[3]: https://www.bloomberg.com/graphics/2017-bitcoin-volume/