Year | Value | 2021 | 7.602688508223 | 2020 | 7.4188077539134 | 2019 | 7.1979784380644 | 2018 | 7.3222312023318 | 2017 | 7.4888702293221 | 2016 | 7.6587256534731 | 2015 | 7.8860215771257 | 2014 | 8.0568357566793 | 2013 | 8.2493123485505 | 2012 | 8.4587723975496 | 2011 | 8.7375461819164 | 2010 | 9.1103594173326 | 2009 | 9.3249273484515 | 2008 | 9.8171524914572 | 2007 | 9.936289025324 | 2006 | 10.18945156416 | 2005 | 10.52638686155 | 2004 | 10.845608268227 | 2003 | 11.145309654169 | 2002 | 11.509293173226 | 2001 | 11.805770481999 | 2000 | 12.112270653283 | 1999 | 12.508733373407 | 1998 | 13.367718094845 | 1997 | 13.389962795858 | 1996 | 13.827380279376 | 1995 | 13.980469601768 | 1994 | 15.114498184666 | 1993 | 14.903178983592 | 1992 | 15.400868095996 | 1991 | 15.775425366049 | 1990 | 15.606264186423 | 1989 | 15.828115788409 | 1988 | 16.935757550268 | 1987 | 16.615542727354 | 1986 | 17.0867171126 | 1985 | 17.67614645012 | 1984 | 18.020038595602 | 1983 | 18.094795878448 | 1982 | 17.46704650307 | 1981 | 17.697101135366 | 1980 | 17.942393689304 | 1979 | 18.275705361985 | 1978 | 18.633488146907 | 1977 | 18.936247540706 | 1976 | 20.185659158136 | 1975 | 20.741960442861 | 1974 | 19.856626633696 | 1973 | 19.814152621766 | 1972 | 20.314888220344 | 1971 | 25.348768247558 | 1970 | 21.658932223987 | 1969 | 20.739476458619 | 1968 | 20.938616222205 | 1967 | 21.230929994427 | 1966 | 21.737914005037 | 1965 | 22.004060822714 | 1964 | 22.034522837202 | 1963 | 22.624602750327 | 1962 | 22.767925326454 | 1961 | 23.166621427729 | 1960 | 23.517922754902 |
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