| 年份 | 进口 | 出口 |
| 2010 | 0.798 | 0.570 |
| 2011 | 0.773 | 0.698 |
| 2012 | 0.780 | 0.691 |
| 2013 | 0.782 | 0.727 |
| 2014 | 0.781 | 0.745 |
| 2015 | 0.798 | 0.757 |
| 2016 | 0.812 | 0.766 |
| 2017 | 0.790 | 0.767 |
| 2018 | 0.792 | 0.767 |
| 2019 | 0.787 | 0.782 |
| 2020 | 0.796 | 0.795 |
| 2021 | 0.779 | 0.796 |
| 2022 | 0.796 | 0.805 |