| Year | Value (SE) |
|---|---|
| 2002 | 0.7069 (0.0725) |
| 2004 | 0.8300 (0.2864) |
| 2005 | 0.4387 (0.1323) |
| 2007 | 0.6905 (0.1169) |
| 2008 | 1.0170 (0.1091) |
| 2009 | 1.0190 (0.1333) |
| 2010 | 0.9065 (0.1006) |
| 2011 | 0.8290 (0.0229) |
| 2012 | 0.7712 (0.0231) |
| 2013 | 0.9068 (0.0710) |
| 2014 | 0.9083 (0.0728) |
| 2015 | 1.2409 (0.6256) |
