| 年份 | 样本(家) | 均值 | 中位数 |
| 2012 | 179 | 4.58% | 2.54% |
| 2013 | 179 | 3.17% | 2.88% |
| 2014 | 179 | 3.84% | 3.75% |
| 2015 | 179 | 5.54% | 3.85% |
| 2016 | 180 | 4.49% | 3.97% |
| 2017 | 179 | 4.18% | 3.60% |
| 2018 | 178 | 5.55% | 4.69% |
| 2019 | 178 | 5.53% | 5.31% |
| 2020 | 179 | 6.56% | 4.86% |
| 2021 | 179 | 7.12% | 5.72% |
| 平均值 | 5.06% | 4.12% |