| Year | Value | | 2022 | 39.866750742527 | | 2021 | 40.257905221298 | | 2020 | 44.424736712467 | | 2019 | 45.5667365669 | | 2018 | 44.466785249325 | | 2017 | 45.38266339911 | | 2016 | 46.716234676567 | | 2015 | 47.348988922032 | | 2014 | 47.21541334094 | | 2013 | 47.07767785667 | | 2012 | 46.163914955236 | | 2011 | 45.852452657172 | | 2010 | 46.029406682547 | | 2009 | 49.032895470698 | | 2008 | 50.064137757829 | | 2007 | 45.902090814147 | | 2006 | 48.013031909038 | | 2005 | 49.745020519643 | | 2004 | 52.317096377672 | | 2003 | 56.949445061337 | | 2002 | 58.022813780001 | | 2001 | 57.854898138802 | | 2000 | 52.359381377074 | | 1999 | 51.286439548042 | | 1998 | 48.946052584807 | | 1997 | 48.540000161437 | | 1996 | 49.37552107423 | | 1995 | 49.119941380311 | | 1994 | 51.138994663961 | | 1993 | 52.635282175503 | | 1992 | 52.155199822892 | | 1991 | 52.490361942788 | | 1990 | 54.094844401445 | | 1989 | 55.559832649633 | | 1988 | 56.318743531534 | | 1987 | 58.643234283582 | | 1986 | 59.252873984843 | | 1985 | 58.146284640309 | | 1984 | 54.148294768322 | | 1983 | 54.430080403595 | | 1982 | 56.465339658399 | | 1981 | 57.311874011597 | | 1980 | 60.147818288648 | | 1979 | 63.801960153634 | | 1978 | 66.793002279494 | | 1977 | 67.98608223467 | | 1976 | 68.603783142488 | | 1975 | 70.555842869318 | | 1974 | 70.68363545677 | | 1973 | 72.377736734772 | | 1972 | 73.54708936078 | | 1971 | 78.341678812104 | | 1970 | 78.978789992006 | | 1969 | 79.196268671403 | | 1968 | 83.596828888278 | | 1967 | 85.865062402702 | | 1966 | 87.08735549994 | | 1965 | 89.207668588283 | | 1964 | 92.492327926348 | | 1963 | 93.054467782129 | | 1962 | 96.560313130115 | | 1961 | 99.342077156406 | | 1960 | 96.954667655511 |
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