| Year | Value | | 2024 | 60.10662831793 | | 2023 | 60.708062920421 | | 2022 | 61.294479283096 | | 2021 | 62.130794114063 | | 2020 | 62.99023284392 | | 2019 | 63.816236173364 | | 2018 | 64.591446119209 | | 2017 | 65.298504698273 | | 2016 | 65.920053927369 | | 2015 | 66.438735823313 | | 2014 | 66.83719240292 | | 2013 | 67.098065683006 | | 2012 | 67.206824787167 | | 2011 | 67.243270422303 | | 2010 | 67.271547418995 | | 2009 | 67.292571142683 | | 2008 | 67.308721379383 | | 2007 | 67.32237791511 | | 2006 | 67.335920535881 | | 2005 | 67.35172902771 | | 2004 | 67.372183176613 | | 2003 | 67.399662768605 | | 2002 | 67.436811583307 | | 2001 | 67.500072161716 | | 2000 | 67.600843114669 | | 1999 | 67.736217059253 | | 1998 | 67.90350755113 | | 1997 | 68.100028145959 | | 1996 | 68.323092399398 | | 1995 | 68.570013867108 | | 1994 | 68.838106104748 | | 1993 | 69.124682667979 | | 1992 | 69.432575301197 | | 1991 | 69.844414992221 | | 1990 | 70.407958786252 | | 1989 | 71.08841250752 | | 1988 | 71.854997856783 | | 1987 | 72.676936534799 | | 1986 | 73.523450242327 | | 1985 | 74.363760680124 | | 1984 | 75.16708954895 | | 1983 | 75.902658549562 | | 1982 | 76.542307505764 | | 1981 | 77.117308921912 | | 1980 | 77.668729138618 | | 1979 | 78.1984467636 | | 1978 | 78.710087776215 | | 1977 | 79.207278155821 | | 1976 | 79.693643881775 | | 1975 | 80.172810933434 |
|