年份 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 合计 |
频数 | 9 | 5 | 8 | 13 | 3 | 11 | 40 | 89 |
比例 | 10.11% | 5.62% | 8.99% | 14.61% | 3.37% | 12.36% | 44.94% | 100% |