Year | Value | 2021 | 9.059701397144 | 2020 | 8.9262765504773 | 2019 | 8.7714762100054 | 2018 | 8.9581694157861 | 2017 | 9.1667143104532 | 2016 | 9.3893600718848 | 2015 | 9.6128599296051 | 2014 | 9.820512735177 | 2013 | 10.057210291691 | 2012 | 10.324578563432 | 2011 | 10.61064499613 | 2010 | 10.942944936359 | 2009 | 11.236883192916 | 2008 | 11.637953808817 | 2007 | 11.967139224422 | 2006 | 12.294961912555 | 2005 | 12.694631002357 | 2004 | 13.092219785577 | 2003 | 13.430196452843 | 2002 | 13.822510121782 | 2001 | 14.156502074375 | 2000 | 14.499995863987 | 1999 | 14.998288777232 | 1998 | 15.926810068409 | 1997 | 15.660520844214 | 1996 | 15.894624723025 | 1995 | 15.971680988376 | 1994 | 15.916425991335 | 1993 | 16.634358897361 | 1992 | 17.130271651568 | 1991 | 17.05987766099 | 1990 | 16.914919551414 | 1989 | 17.008037547143 | 1988 | 18.28127285847 | 1987 | 17.760151919189 | 1986 | 17.404978663989 | 1985 | 17.906602966103 | 1984 | 18.073300904683 | 1983 | 17.917417586184 | 1982 | 17.817595414028 | 1981 | 17.981027571462 | 1980 | 18.185466388282 | 1979 | 18.377886547456 | 1978 | 18.633939594912 | 1977 | 18.852327612097 | 1976 | 19.266242931111 | 1975 | 19.705583080476 | 1974 | 20.05431114646 | 1973 | 20.434806607362 | 1972 | 21.177836580033 | 1971 | 21.373388902982 | 1970 | 21.902711784157 | 1969 | 22.365043057696 | 1968 | 22.610558366967 | 1967 | 23.075320012081 | 1966 | 23.090697902696 | 1965 | 23.276350491837 | 1964 | 23.417690869054 | 1963 | 23.782872273334 | 1962 | 24.01068296272 | 1961 | 24.395555389822 | 1960 | 24.614521142082 |
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