| Year | Value (SE) |
|---|---|
| 2009 | 0.8530 (0.0254) |
| 2010 | 0.7590 (0.0312) |
| 2011 | 0.8270 (0.0134) |
| 2012 | 0.7970 (0.0100) |
| 2013 | 0.7340 (0.0293) |
| 2014 | 0.7860 (0.0220) |
| 2015 | 0.7300 (0.0352) |
| 2016 | 0.6380 (0.0056) |
| 2017 | 0.7770 (0.0093) |
| 2018 | 0.7700 (0.0086) |
| 2019 | 0.7490 (0.0079) |
| 2020 | 0.6030 (0.0075) |
| 2021 | 0.7450 (0.0088) |
| 2022 | 0.6690 (0.0099) |
| 2023 | 0.7280 (0.0075) |
| 2024 | 0.7270 (0.0141) |
