The graph below shows the market share of the most popular bitcoin mining pools :
Antpool - 21.2%
BTC.top - 11.6%
BTC.com - 9.9%
ViaBTC - 7.3%
BTCC pool - 6.1%
F2pool - 6%
Bixin - 5.8%
The total from the following pools is 70%.
Which shows the clear dominance in the bitcoin mining . China being the largest supplier of Mining hardwares and equipment and as electricity is quite cheap in China , it became the world largest bitcoin miner.