Year | Value | 2021 | 31.959960675664 | 2020 | 31.620341406739 | 2019 | 31.361158280454 | 2018 | 31.361158280454 | 2017 | 31.173473947627 | 2016 | 30.601483599964 | 2015 | 30.163553490035 | 2014 | 30.163553490035 | 2013 | 30.118866744124 | 2012 | 30.011618553937 | 2011 | 29.591563142372 | 2010 | 29.207257127536 | 2009 | 28.58164268478 | 2008 | 28.456519796228 | 2007 | 28.242023415855 | 2006 | 28.242023415855 | 2005 | 28.152649924032 | 2004 | 28.06327643221 | 2003 | 28.179461971579 | 2002 | 27.0622933238 | 2001 | 26.240057199035 | 2000 | 26.231119849853 | 1999 | 29.82393422111 | 1998 | 30.34230047368 | 1997 | 30.34230047368 | 1996 | 31.101975154169 | 1995 | 31.101975154169 | 1994 | 31.459469121459 | 1993 | 31.709714898561 | 1992 | 29.98480650639 | 1991 | 29.868620967021 | 1990 | 29.671999285012 | 1989 | 30.127804093306 | 1988 | 29.359192063634 | 1987 | 29.359192063634 | 1986 | 29.359192063634 | 1985 | 29.296630619358 | 1984 | 29.287693270176 | 1983 | 29.2251318259 | 1982 | 29.216194476718 | 1981 | 29.171507730807 | 1980 | 29.108946286531 | 1979 | 29.108946286531 | 1978 | 29.108946286531 | 1977 | 29.001698096345 | 1976 | 28.331396907677 | 1975 | 28.018589686299 | 1974 | 27.670033068192 | 1973 | 27.616408973099 | 1972 | 27.527035481276 | 1971 | 27.214228259898 | 1970 | 27.169541513987 | 1969 | 27.080168022165 | 1968 | 27.080168022165 | 1967 | 27.035481276253 | 1966 | 26.946107784431 | 1965 | 26.856734292609 | 1964 | 26.812047546698 | 1963 | 26.767360800786 | 1962 | 26.722674054875 | 1961 | 26.633300563053 |
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