| Year | Operating income | Business tax and additional | Tax rate |
| 2012 | 62541346.79 | 1845297.36 | 2.95% |
| 2013 | 64185675.98 | 1651223.72 | 2.57% |
| 2014 | 67320754.37 | 1615537.48 | 2.40% |
| 2015 | 68983295.81 | 1757629.03 | 2.55% |