| Year | Value | | 2022 | 62.839749933514 | | 2021 | 62.689995568653 | | 2020 | 62.561454243107 | | 2019 | 62.438139213102 | | 2018 | 62.333666603585 | | 2017 | 62.248454729263 | | 2016 | 62.184484322993 | | 2015 | 62.140672458208 | | 2014 | 62.113645142774 | | 2013 | 62.096813736679 | | 2012 | 62.081776973887 | | 2011 | 62.063934485231 | | 2010 | 62.02606502442 | | 2009 | 61.986046876009 | | 2008 | 61.92454054662 | | 2007 | 61.841845428767 | | 2006 | 61.763895445527 | | 2005 | 61.70269222419 | | 2004 | 61.648181049058 | | 2003 | 61.602155691992 | | 2002 | 61.555760747199 | | 2001 | 61.4954533011 | | 2000 | 61.476187357498 | | 1999 | 61.505069788599 | | 1998 | 61.534018233525 | | 1997 | 61.563177944304 | | 1996 | 61.587247657553 | | 1995 | 61.60923061256 | | 1994 | 61.636753601516 | | 1993 | 61.665238651562 | | 1992 | 61.69341933307 | | 1991 | 61.603312369399 | | 1990 | 61.391848910508 | | 1989 | 61.183139288669 | | 1988 | 60.891727385006 | | 1987 | 60.509667320532 | | 1986 | 60.131109502475 | | 1985 | 59.746707855313 | | 1984 | 59.352577733088 | | 1983 | 58.955344885466 | | 1982 | 58.55863251781 | | 1981 | 58.163953862176 | | 1980 | 57.706124522697 | | 1979 | 57.104057934999 | | 1978 | 56.43427635979 | | 1977 | 55.705067734602 | | 1976 | 54.99225445967 | | 1975 | 54.294466180797 | | 1974 | 53.585430053964 | | 1973 | 52.865958331873 | | 1972 | 52.146468990927 | | 1971 | 51.42665617342 | | 1970 | 50.780276186764 | | 1969 | 50.215152913846 | | 1968 | 49.638503939877 | | 1967 | 49.067806458233 | | 1966 | 48.50539627872 | | 1965 | 47.881130033419 | | 1964 | 47.209693854483 | | 1963 | 46.534920892256 | | 1962 | 45.867368518493 | | 1961 | 45.207338073743 | | 1960 | 44.50789271439 |
|