| Year | Value (SE) |
|---|---|
| 2000 | 0.6840 (0.0850) |
| 2001 | 0.8130 (0.0137) |
| 2002 | 1.0140 (0.0300) |
| 2003 | 0.8630 (0.0636) |
| 2004 | 0.9200 (0.0540) |
| 2005 | 0.8740 (0.0318) |
| 2006 | 0.9350 (0.0433) |
| 2007 | 0.9930 (0.0570) |
| 2008 | 1.0090 (0.0513) |
| 2009 | 1.0390 (0.0607) |
| 2010 | 1.2360 (0.1773) |
| 2011 | 1.0270 (0.0584) |
| 2012 | 0.9470 (0.0468) |
| 2013 | 1.0600 (0.0959) |
| 2014 | 0.9310 (0.0695) |
| 2015 | 1.0390 (0.2352) |
| 2016 | 0.8200 (0.0413) |
| 2019 | 0.8960 (0.0826) |
| 2020 | 1.4770 (0.3081) |
| 2021 | 1.8100 (1.9435) |
| 2022 | 1.0660 (0.2142) |
| 2023 | 0.8010 (0.0996) |
