| Year | Value (SE) |
|---|---|
| 2008 | 0.7908 (0.1798) |
| 2009 | 0.7466 (0.0971) |
| 2010 | 0.7881 (0.1614) |
| 2011 | 0.8390 (0.0732) |
| 2012 | 0.9025 (0.0849) |
| 2013 | 0.9835 (0.1464) |
| 2014 | 0.6935 (0.1096) |
| 2015 | 0.5561 (0.1304) |
| 2016 | 0.8343 (0.0970) |
| 2018 | 0.8081 (0.2109) |
| 2019 | 0.5800 (0.1495) |
| 2020 | 1.1162 (0.6676) |
| 2022 | 0.7084 (0.3168) |
| 2023 | 1.0301 (0.3530) |
