| Year | Value | | 2022 | 68.048503788373 | | 2021 | 67.860141737412 | | 2020 | 67.717997943344 | | 2019 | 67.972588663144 | | 2018 | 67.881638149994 | | 2017 | 67.711812261196 | | 2016 | 67.599727495782 | | 2015 | 67.2719360091 | | 2014 | 67.09847173181 | | 2013 | 66.628801595293 | | 2012 | 66.136305481799 | | 2011 | 65.333756592754 | | 2010 | 64.195587544273 | | 2009 | 63.525492879255 | | 2008 | 62.695624817447 | | 2007 | 60.591030381201 | | 2006 | 59.486439297226 | | 2005 | 58.944070406262 | | 2004 | 58.530662083936 | | 2003 | 58.252964542711 | | 2002 | 58.119062889671 | | 2001 | 57.851508329517 | | 2000 | 57.20017833259 | | 1999 | 57.320823155103 | | 1998 | 57.708399773792 | | 1997 | 58.098002910676 | | 1996 | 59.173611815521 | | 1995 | 59.435568125208 | | 1994 | 59.946721260158 | | 1993 | 60.434703128984 | | 1992 | 60.682457369155 | | 1991 | 60.265255128994 |
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