China recently cracked down on BTC, so that was a big punch in the gut to its growth there.

http://www.bloomberg.com/news/2013-12-05/china-s-pboc-bans-financial-companies-from-bitcoin-transactions.html

which led to

http://www.nytimes.com/2013/12/19/business/international/china-bitcoin-exchange-ends-renminbi-deposits.html