| Year | Value (SE) |
|---|---|
| 2008 | 0.5030 (0.0627) |
| 2009 | 0.7438 (0.0346) |
| 2011 | 0.6336 (0.0183) |
| 2012 | 0.6011 (0.0291) |
| 2013 | 0.5926 (0.0742) |
| 2014 | 0.7250 (0.0655) |
| 2015 | 1.0927 (0.2962) |
| 2016 | 0.6360 (0.0398) |
| 2018 | 0.7692 (0.0526) |
| 2019 | 0.7535 (0.0292) |
| 2020 | 0.7535 (0.1690) |
| 2021 | 1.4677 (0.8172) |
| 2022 | 0.7056 (0.2016) |
| 2023 | 1.1081 (0.3236) |
