Year | Value | 2015 | 19.521064474538 | 2014 | 21.832551336758 | 2013 | 25.602640230115 | 2012 | 27.176671678485 | 2011 | 28.438587221214 | 2010 | 29.722733049253 | 2009 | 28.855225710769 | 2008 | 31.20615283509 | 2007 | 32.71270239411 | 2006 | 32.578134303191 | 2005 | 33.06769583823 | 2004 | 32.543557014244 | 2003 | 31.795014116049 | 2002 | 30.138221865189 | 2001 | 29.29922729319 | 2000 | 30.248330251801 | 1999 | 29.619193557896 | 1998 | 28.156085880076 | 1997 | 28.342213181793 | 1996 | 28.317063050925 | 1995 | 28.199510293227 | 1994 | 28.165091615109 | 1993 | 29.451999948642 | 1992 | 28.553346671889 | 1991 | 28.995969657081 | 1990 | 28.5630646452 | 1989 | 27.66208294442 | 1988 | 26.56489291591 | 1987 | 25.093075206767 | 1986 | 24.733984886421 | 1985 | 24.512858819943 | 1984 | 25.159013229559 | 1983 | 26.713326824062 | 1982 | 26.305202697037 | 1981 | 28.639529225086 | 1980 | 31.353898485208 | 1979 | 34.485959275753 | 1978 | 36.569659379178 | 1977 | 36.15354712302 | 1976 | 36.927171862869 | 1975 | 33.840607736133 | 1974 | 35.877703381844 | 1973 | 36.091718280407 | 1972 | 33.578583298187 | 1971 | 31.970944832783 | 1970 | 30.650103790367 | 1969 | 30.562808467026 | 1968 | 27.830029709698 | 1967 | 25.780298675432 | 1966 | 25.663110051188 | 1965 | 24.823613556377 | 1964 | 23.109247086357 | 1963 | 22.196528329801 | 1962 | 19.975157968002 | 1961 | 18.655149636936 | 1960 | 17.743621562683 |
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