| 年份 | 样本(家) | 均值 | 中位数 |
| 2012 | 179 | 3.75% | 2.09% |
| 2013 | 179 | 2.67% | 2.44% |
| 2014 | 179 | 3.23% | 3.23% |
| 2015 | 179 | 4.67% | 3.21% |
| 2016 | 180 | 3.79% | 3.38% |
| 2017 | 179 | 3.54% | 3.06% |
| 2018 | 178 | 4.58% | 3.88% |
| 2019 | 178 | 4.62% | 4.43% |
| 2020 | 179 | 5.52% | 3.96% |
| 2021 | 179 | 5.90% | 4.63% |
| 平均值 |
| 4.23% | 3.43% |