| Region | 2012 | 2013 | 2014 | 2015 |
| Jiangsu | 2.73% | 2.65% | 2.43% | 2.17% |
| Zhejiang | 2.85% | 2.97% | 2.76% | 2.73% |
| Shandong | 3.11% | 3.18% | 3.04% | 2.57% |
| Guangdong | 2.62% | 2.35% | 1.91% | 1.99% |