| Year | Value (SE) |
|---|---|
| 2005 | 0.9030 (0.2603) |
| 2006 | 0.9110 (0.0458) |
| 2007 | 0.8390 (0.4766) |
| 2008 | 0.7970 (0.1420) |
| 2009 | 0.9130 (0.0424) |
| 2010 | 1.3750 (0.2061) |
| 2011 | 0.8960 (0.0293) |
| 2012 | 0.8610 (0.0279) |
| 2013 | 0.9610 (0.0725) |
| 2014 | 0.9970 (0.0911) |
| 2016 | 0.9450 (0.0382) |
| 2017 | 0.9130 (0.0358) |
| 2018 | 0.9320 (0.0448) |
| 2019 | 0.9050 (0.0382) |
| 2020 | 0.5130 (0.1227) |
| 2021 | 1.2570 (0.4207) |
| 2022 | 1.1430 (0.2784) |
| 2023 | 0.8070 (0.1118) |
| 2024 | 1.2230 (0.5524) |
