| Year | Value (SE) |
|---|---|
| 2003 | 0.9940 (0.2034) |
| 2004 | 0.5910 (0.1724) |
| 2006 | 0.8180 (0.2050) |
| 2008 | 1.0850 (0.2119) |
| 2009 | 0.8280 (0.1668) |
| 2010 | 1.0690 (0.1167) |
| 2011 | 1.2540 (0.1510) |
| 2012 | 0.8670 (0.1100) |
| 2013 | 0.8320 (0.0931) |
| 2014 | 0.8390 (0.0732) |
| 2016 | 0.7930 (0.0513) |
| 2017 | 1.0640 (0.1504) |
| 2018 | 0.9530 (0.1925) |
| 2019 | 0.9380 (0.2586) |
