| Year | Value (SE) |
|---|---|
| 2008 | 0.8322 (0.0921) |
| 2009 | 0.7553 (0.0721) |
| 2010 | 0.7567 (0.1262) |
| 2011 | 0.8818 (0.0498) |
| 2013 | 0.5884 (0.1141) |
| 2014 | 0.8437 (0.1726) |
| 2015 | 0.5405 (0.2817) |
| 2016 | 0.5612 (0.0733) |
| 2017 | 0.6834 (0.0715) |
| 2018 | 0.6815 (0.1511) |
| 2019 | 0.9121 (0.1705) |
| 2020 | 0.6546 (0.3612) |
| 2021 | 0.5505 (0.2374) |
| 2023 | 0.7915 (0.2994) |
| 2024 | 0.7712 (0.5177) |
| 2025 | 0.6420 (0.5317) |
