| Year | Value | | 2021 | 62.764094143404 | | 2020 | 62.39846743295 | | 2019 | 62.032840722496 | | 2018 | 61.667214012042 | | 2017 | 61.301587301587 | | 2016 | 60.935960591133 | | 2015 | 60.570333880679 | | 2014 | 60.204926108374 | | 2013 | 59.83951833607 | | 2012 | 59.474110563766 | | 2011 | 59.108702791461 | | 2010 | 58.743295019157 | | 2009 | 58.377832512315 | | 2008 | 58.012370005473 | | 2007 | 57.646907498632 | | 2006 | 57.28144499179 | | 2005 | 56.915982484948 | | 2004 | 56.550519978106 | | 2003 | 56.185057471264 | | 2002 | 55.819594964422 | | 2001 | 55.454132457581 | | 2000 | 55.088669950739 | | 1999 | 54.72315270936 | | 1998 | 54.35763546798 | | 1997 | 53.992118226601 | | 1996 | 53.626600985222 | | 1995 | 53.261083743842 | | 1994 | 52.895566502463 | | 1993 | 52.530049261084 | | 1992 | 52.164532019704 | | 1991 | 51.799014778325 | | 1990 | 51.433497536946 |
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