| Year | Value | | 2022 | 72.510001402534 | | 2021 | 72.675007951314 | | 2020 | 72.648960199393 | | 2019 | 73.23704641756 | | 2018 | 74.260716252966 | | 2017 | 74.916059894791 | | 2016 | 75.352790534401 | | 2015 | 75.258896707617 | | 2014 | 74.592824903532 | | 2013 | 74.050565438189 | | 2012 | 74.262827576798 | | 2011 | 74.875385980597 | | 2010 | 75.749224979924 | | 2009 | 76.605782618362 | | 2008 | 76.432567990766 | | 2007 | 74.792291213604 | | 2006 | 71.680097728213 | | 2005 | 68.265720917628 | | 2004 | 67.190912444742 | | 2003 | 67.437827727865 | | 2002 | 67.377093773574 | | 2001 | 67.291564468918 | | 2000 | 67.16057448327 | | 1999 | 67.008423256405 | | 1998 | 66.829432854214 | | 1997 | 66.645658937396 | | 1996 | 66.620502016948 | | 1995 | 66.7481990088 | | 1994 | 66.881639680197 | | 1993 | 67.023563855724 | | 1992 | 67.174772381512 | | 1991 | 67.334376081632 | | 1990 | 67.505745174619 | | 1989 | 67.69189685544 | | 1988 | 67.894560612604 | | 1987 | 68.118049981001 | | 1986 | 68.320656608985 | | 1985 | 68.323275060951 | | 1984 | 68.147920549275 | | 1983 | 67.961047528552 | | 1982 | 67.752264817279 | | 1981 | 67.508910192718 | | 1980 | 67.218958370878 | | 1979 | 66.870352731518 | | 1978 | 66.451991593603 | | 1977 | 65.957381248982 | | 1976 | 65.375610218494 | | 1975 | 64.687786795732 | | 1974 | 63.868175505719 | | 1973 | 62.878815640001 | | 1972 | 61.678059566665 | | 1971 | 60.198653603414 | | 1970 | 58.339759505792 | | 1969 | 57.060573877934 | | 1968 | 56.682290210918 | | 1967 | 56.229625410521 | | 1966 | 55.70572624552 | | 1965 | 55.126999059266 | | 1964 | 54.464549547201 | | 1963 | 53.682041216879 | | 1962 | 52.786827116991 | | 1961 | 51.798758445314 | | 1960 | 50.957812285282 |
|