| Year | Value | | 2022 | 62.331183668704 | | 2021 | 62.02650424878 | | 2020 | 61.717344429007 | | 2019 | 61.417445402604 | | 2018 | 61.121945905021 | | 2017 | 60.820287072961 | | 2016 | 60.516808500414 | | 2015 | 60.185203004001 | | 2014 | 59.777099283704 | | 2013 | 59.395867001728 | | 2012 | 59.072077397551 | | 2011 | 58.852916584913 | | 2010 | 58.633310251823 | | 2009 | 58.294025744249 | | 2008 | 57.948235716979 | | 2007 | 57.615575740394 | | 2006 | 57.281170861598 | | 2005 | 56.901412349823 | | 2004 | 56.516069670592 | | 2003 | 56.165302396741 | | 2002 | 55.828000685703 | | 2001 | 55.484478669268 | | 2000 | 55.121471004047 | | 1999 | 54.756632632043 | | 1998 | 54.393678621994 | | 1997 | 54.036791888484 | | 1996 | 53.704137615426 | | 1995 | 53.376288910903 | | 1994 | 53.028579899834 | | 1993 | 52.619758701524 | | 1992 | 52.199199950552 | | 1991 | 51.794601189838 | | 1990 | 51.457779837696 | | 1989 | 51.123506960107 | | 1988 | 50.785108222725 | | 1987 | 50.42317660275 | | 1986 | 49.971101645722 | | 1985 | 49.461348363102 | | 1984 | 48.95607207769 | | 1983 | 48.421635649301 | | 1982 | 47.890810787568 | | 1981 | 47.347463335941 | | 1980 | 46.793072071299 | | 1979 | 46.249799876089 | | 1978 | 45.769501524116 | | 1977 | 45.277438075833 | | 1976 | 44.664032044813 | | 1975 | 44.001998074784 | | 1974 | 43.377493928988 | | 1973 | 42.745659185517 | | 1972 | 42.09472508165 | | 1971 | 41.445325785233 | | 1970 | 40.807044349913 | | 1969 | 40.143742841802 | | 1968 | 39.481947482653 | | 1967 | 38.821703646746 | | 1966 | 38.182354560834 | | 1965 | 37.460415315053 | | 1964 | 36.689600287096 | | 1963 | 35.950893252865 | | 1962 | 35.220229251724 | | 1961 | 34.496314009561 | | 1960 | 33.776503946001 |
|