| Year | Value (SE) |
|---|---|
| 2006 | 0.4169 (0.0457) |
| 2007 | 0.6327 (0.1102) |
| 2008 | 0.4044 (0.0658) |
| 2009 | 0.2849 (0.0304) |
| 2010 | 0.6320 (0.1053) |
| 2011 | 0.2825 (0.0287) |
| 2012 | 0.5762 (0.0333) |
| 2013 | 0.5264 (0.0560) |
| 2014 | 0.4283 (0.0473) |
| 2015 | 0.3950 (0.0939) |
| 2016 | 0.4169 (0.0351) |
| 2017 | 0.4258 (0.0505) |
| 2018 | 0.5089 (0.0629) |
| 2019 | 0.2523 (0.0658) |
| 2020 | 0.3696 (0.1323) |
| 2021 | 0.6394 (0.4942) |
| 2022 | 0.8154 (0.3508) |
| 2023 | 0.4201 (0.0836) |
| 2024 | 0.3346 (0.1713) |
