| Year | Value | | 2022 | 2.6657111351328 | | 2021 | 3.5432341109722 | | 2020 | 3.7353518916131 | | 2019 | 3.9104953249545 | | 2018 | 3.7036783972685 | | 2017 | 3.9976808553134 | | 2016 | 4.2714966180488 | | 2015 | 9.8063756564058 | | 2014 | 4.5140293230086 | | 2013 | 5.1551393946578 | | 2012 | 5.0472040950378 | | 2011 | 4.3469297658496 | | 2010 | 5.2202192314878 | | 2009 | 4.3753556961881 | | 2008 | 7.1465401761963 | | 2007 | 8.2011049612153 | | 2006 | 7.3531330443661 | | 2005 | 8.200930808491 | | 2004 | 9.544479119677 | | 2003 | 8.9607912763188 | | 2002 | 7.970671028375 | | 2001 | 7.8690601386221 | | 2000 | 6.4848522758074 | | 1999 | 7.2969958753032 |
|