| Year | Value (SE) |
|---|---|
| 2001 | 0.4380 (0.0369) |
| 2002 | 0.5520 (0.0425) |
| 2010 | 0.5600 (0.0233) |
| 2011 | 0.7630 (0.0547) |
| 2012 | 0.5230 (0.0706) |
| 2013 | 0.3470 (0.0369) |
| 2014 | 0.4200 (0.0332) |
| 2015 | 0.4290 (0.0649) |
| 2016 | 0.5130 (0.0513) |
| 2017 | 0.4810 (0.0569) |
| 2018 | 0.7870 (0.0702) |
| 2020 | 0.8160 (0.0466) |
| 2021 | 0.8750 (0.0353) |
| 2022 | 0.8910 (0.0493) |
| 2023 | 0.8820 (0.0511) |
