| Year | |
|---|---|
| 1997 | 79.9 |
| 1998 | 87.7 |
| 1999 | 54.0 |
| 2000 | 62.3 |
| 2001 | 64.1 |
| 2002 | 60.8 |
| 2003 | 62.3 |
| 2004 | 62.1 |
| 2005 | 54.6 |
| 2006 | 51.3 |
| 2007 | 53.7 |
| 2008 | 53.7 |
| 2009 | 52.7 |
| 2010 | 52.3 |
| 2011 | 52.2 |
| 2012 | 53.1 |
| 2013 | 55.2 |
| 2014 | 59.6 |
| 2015 | 59.7 |
| 2016 | 59.5 |
| 2017 | 60.3 |
| 2018 | 64.0 |
| 2019 | 65.2 |
| 2020 | 66.5 |
| 2021 | 72.9 |
| 2022 | 73.4 |
| 2023 | 71.8 |
| 2024 | 71.1 |