Year | Value | 2021 | 18.336560883427 | 2020 | 18.516246909994 | 2019 | 18.932680974298 | 2018 | 19.430374561309 | 2017 | 19.678024939877 | 2016 | 20.226961822158 | 2015 | 20.495524546097 | 2014 | 20.838247768212 | 2013 | 21.6234411944 | 2012 | 22.057750665729 | 2011 | 22.507411351797 | 2010 | 22.97726724665 | 2009 | 23.443880185725 | 2008 | 23.803328177963 | 2007 | 24.279270997245 | 2006 | 24.720995913788 | 2005 | 25.399664829333 | 2004 | 26.184349548673 | 2003 | 26.825049595544 | 2002 | 27.499245850548 | 2001 | 28.093067546476 | 2000 | 28.400039415707 | 1999 | 28.713198737653 | 1998 | 29.220846854718 | 1997 | 29.706448484006 | 1996 | 30.178641396255 | 1995 | 30.746851853935 | 1994 | 31.28527841593 | 1993 | 31.696003423357 | 1992 | 32.336689296305 | 1991 | 32.882705508197 | 1990 | 33.384655981216 | 1989 | 34.108799810733 | 1988 | 34.678448400572 | 1987 | 35.220685393696 | 1986 | 35.950643160541 | 1985 | 36.172415659437 | 1984 | 36.677166963258 | 1983 | 36.949834197094 | 1982 | 37.325429427667 | 1981 | 37.689114914462 | 1980 | 37.832298151083 | 1979 | 37.892140456094 | 1978 | 37.992864751272 | 1977 | 38.406107284617 | 1976 | 39.007948804651 | 1975 | 39.223134164341 | 1974 | 39.814034447822 | 1973 | 40.119847805942 | 1972 | 40.349534205102 | 1971 | 40.591590020249 | 1970 | 40.689602611216 | 1969 | 40.928327241377 | 1968 | 41.310980572989 | 1967 | 41.666865198569 | 1966 | 41.939261555315 | 1965 | 42.33587157623 | 1964 | 42.69962873282 | 1963 | 42.905889816373 | 1962 | 43.115717176433 | 1961 | 43.284965967056 | 1960 | 43.445317966076 |
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