| Year | Value (SE) |
|---|---|
| 2000 | 2.3930 (1.6853) |
| 2001 | 0.4930 (0.1250) |
| 2008 | 0.8800 (0.0412) |
| 2009 | 0.8990 (0.0482) |
| 2010 | 0.8540 (0.0306) |
| 2011 | 0.8860 (0.0457) |
| 2012 | 0.9620 (0.0619) |
| 2013 | 0.9390 (0.0774) |
| 2014 | 0.9950 (0.0756) |
| 2015 | 0.7750 (0.1283) |
| 2016 | 1.0430 (0.0632) |
| 2017 | 0.8100 (0.0511) |
| 2018 | 0.9370 (0.0809) |
| 2019 | 0.9950 (0.0743) |
| 2020 | 1.2940 (0.1746) |
| 2021 | 0.7030 (0.1143) |
| 2022 | 0.9040 (0.2718) |
| 2023 | 0.7710 (0.0946) |
