| Year | Value (SE) |
|---|---|
| 2007 | 0.9310 (0.1288) |
| 2009 | 0.9600 (0.1133) |
| 2010 | 0.9920 (0.1514) |
| 2011 | 1.1510 (0.1862) |
| 2012 | 0.9500 (0.1569) |
| 2013 | 2.2680 (1.6435) |
| 2014 | 3.2900 (1.9327) |
| 2015 | 1.3120 (0.6045) |
| 2017 | 0.8550 (0.0947) |
| 2018 | 0.7370 (0.1724) |
| 2019 | 0.8490 (0.1049) |
| 2020 | 1.3810 (0.2815) |
| 2021 | 0.9940 (0.2556) |
| 2023 | 1.1060 (0.1726) |
