| Year | Value (SE) |
|---|---|
| 2007 | 0.8473 (0.1048) |
| 2009 | 0.6963 (0.1372) |
| 2010 | 0.8148 (0.1289) |
| 2011 | 0.9235 (0.1619) |
| 2012 | 0.8836 (0.0889) |
| 2013 | 0.6057 (0.1049) |
| 2014 | 0.6868 (0.0907) |
| 2015 | 0.2964 (0.1358) |
| 2016 | 0.7725 (0.1011) |
| 2018 | 0.9472 (0.2180) |
| 2019 | 0.6376 (0.1383) |
| 2020 | 1.6435 (0.6252) |
| 2021 | 0.6618 (0.6986) |
| 2022 | 0.6917 (0.8723) |
| 2023 | 0.5597 (0.1918) |
