| Year | Value (SE) |
|---|---|
| 2008 | 0.6810 (0.0806) |
| 2009 | 0.9520 (0.0357) |
| 2010 | 1.0424 (0.0885) |
| 2011 | 0.9338 (0.0305) |
| 2012 | 0.8936 (0.0281) |
| 2013 | 0.9345 (0.0511) |
| 2014 | 0.9727 (0.0542) |
| 2015 | 1.0819 (0.1534) |
| 2016 | 0.8321 (0.0337) |
| 2017 | 0.8240 (0.0379) |
| 2018 | 0.8203 (0.0352) |
| 2019 | 0.9206 (0.0389) |
| 2020 | 1.1761 (0.1935) |
| 2021 | 0.8967 (0.2307) |
| 2022 | 0.8161 (0.1297) |
| 2023 | 0.8304 (0.0665) |
| 2024 | 0.7972 (0.2528) |
