| Year | Value | | 2021 | 46.961161858028 | | 2020 | 46.719001751593 | | 2019 | 46.476841645157 | | 2018 | 46.234681538722 | | 2017 | 45.996336984649 | | 2016 | 45.878354877516 | | 2015 | 44.871164038892 | | 2014 | 44.442848891569 | | 2013 | 44.063952112559 | | 2012 | 43.570824706419 | | 2011 | 43.164732319557 | | 2010 | 42.733215446194 | | 2009 | 42.29306629322 | | 2008 | 41.776221898258 | | 2007 | 41.294326173062 | | 2006 | 40.750254959318 | | 2005 | 40.232069735997 | | 2004 | 40.073802689715 | | 2003 | 39.556513045441 | | 2002 | 38.978882627596 | | 2001 | 38.395628274776 | | 2000 | 37.883688034463 | | 1999 | 35.464333773695 | | 1998 | 34.724483087038 | | 1997 | 33.984632400381 | | 1996 | 33.244781713724 | | 1995 | 32.504931027067 | | 1994 | 31.76508034041 | | 1993 | 31.025229653753 | | 1992 | 30.285378967096 | | 1991 | 29.545528280439 | | 1990 | 28.805677593782 |
|