| Year | |
|---|---|
| 1997 | 47.0 |
| 1998 | 47.9 |
| 1999 | 32.1 |
| 2000 | 36.3 |
| 2001 | 38.5 |
| 2002 | 46.6 |
| 2003 | 56.0 |
| 2004 | 59.3 |
| 2005 | 64.8 |
| 2006 | 70.1 |
| 2007 | 73.7 |
| 2008 | 72.7 |
| 2009 | 69.6 |
| 2010 | 70.3 |
| 2011 | 72.5 |
| 2012 | 76.8 |
| 2013 | 78.9 |
| 2014 | 74.2 |
| 2015 | 73.1 |
| 2016 | 64.4 |
| 2017 | 60.7 |
| 2018 | 59.7 |
| 2019 | 63.6 |
| 2020 | 56.1 |
| 2021 | 63.0 |
| 2022 | 62.3 |
| 2023 | 63.8 |
| 2024 | 64.8 |