| Year | Value (SE) |
|---|---|
| 2007 | 0.3550 (0.0398) |
| 2009 | 0.4640 (0.0485) |
| 2010 | 0.5620 (0.0679) |
| 2011 | 0.4480 (0.0649) |
| 2012 | 0.4380 (0.0594) |
| 2013 | 0.9260 (0.6351) |
| 2014 | 0.7440 (0.4132) |
| 2015 | 0.5410 (0.2330) |
| 2017 | 0.2960 (0.0225) |
| 2018 | 0.5230 (0.0722) |
| 2019 | 0.3310 (0.0248) |
| 2020 | 0.4830 (0.0560) |
| 2021 | 0.6110 (0.1102) |
| 2023 | 0.4210 (0.0390) |
