| Year | Value (SE) |
|---|---|
| 2000 | 0.8240 (0.0265) |
| 2001 | 0.9620 (0.0047) |
| 2002 | 0.9510 (0.0226) |
| 2003 | 0.9020 (0.0272) |
| 2004 | 0.9120 (0.0117) |
| 2005 | 0.9200 (0.0095) |
| 2006 | 0.8270 (0.0183) |
| 2007 | 0.9080 (0.0253) |
| 2008 | 0.9620 (0.0217) |
| 2009 | 0.9670 (0.0259) |
| 2010 | 1.0470 (0.0657) |
| 2011 | 0.9400 (0.0237) |
| 2012 | 0.8630 (0.0181) |
| 2013 | 1.0110 (0.0622) |
| 2014 | 1.0550 (0.0380) |
| 2015 | 0.8800 (0.0839) |
| 2016 | 0.9510 (0.0204) |
| 2019 | 0.9190 (0.0659) |
| 2020 | 0.8940 (0.1372) |
| 2021 | 0.6590 (0.2358) |
| 2022 | 0.7970 (0.1207) |
| 2023 | 0.9560 (0.0572) |
