| Year | Value (SE) |
|---|---|
| 2007 | 0.3820 (0.0324) |
| 2009 | 0.4830 (0.0290) |
| 2010 | 0.5660 (0.0541) |
| 2011 | 0.3890 (0.0299) |
| 2012 | 0.4610 (0.0448) |
| 2013 | 0.4080 (0.0968) |
| 2014 | 0.2260 (0.0444) |
| 2015 | 0.4120 (0.0686) |
| 2017 | 0.3460 (0.0285) |
| 2018 | 0.7100 (0.1343) |
| 2019 | 0.3900 (0.0387) |
| 2020 | 0.3500 (0.0591) |
| 2021 | 0.6150 (0.1129) |
| 2023 | 0.3810 (0.0483) |
