| Year | Value (SE) |
|---|---|
| 2000 | 0.8090 (0.0163) |
| 2002 | 0.9250 (0.0170) |
| 2003 | 0.9110 (0.0164) |
| 2004 | 0.9190 (0.0069) |
| 2005 | 0.9230 (0.0053) |
| 2006 | 0.8150 (0.0088) |
| 2007 | 0.9320 (0.0120) |
| 2008 | 0.8960 (0.0207) |
| 2009 | 0.9940 (0.0186) |
| 2010 | 0.9360 (0.0266) |
| 2011 | 0.9140 (0.0115) |
| 2012 | 0.8600 (0.0121) |
| 2013 | 0.9750 (0.0279) |
| 2014 | 0.9730 (0.0191) |
| 2015 | 1.0280 (0.0547) |
| 2016 | 0.9400 (0.0160) |
| 2017 | 0.7090 (0.0193) |
| 2020 | 0.9000 (0.0879) |
| 2021 | 0.8880 (0.2033) |
| 2022 | 0.7260 (0.1246) |
| 2023 | 0.9610 (0.0525) |
