| Year | Value | | 2022 | 0.13388452776164 | | 2021 | 0.17534507491275 | | 2020 | 0.23518286529114 | | 2019 | 0.25269123727425 | | 2018 | 0.32332135460703 | | 2017 | 0.41152598020106 | | 2016 | 0.44377193929386 | | 2015 | 0.47549651695853 | | 2014 | 0.54800516489953 | | 2013 | 0.60774627656548 | | 2012 | 0.64434461278447 | | 2011 | 0.64585745072644 | | 2010 | 0.6714033039228 | | 2009 | 0.71838136464921 | | 2008 | 0.74762381126891 | | 2007 | 0.76191607845988 | | 2006 | 0.75399428433537 | | 2005 | 0.7781388644213 | | 2004 | 0.82130942426996 | | 2003 | 0.85950605725606 | | 2002 | 0.89572340321822 | | 2001 | 0.92062697872979 | | 2000 | 0.99428069309597 | | 1999 | 1.1232036486235 | | 1998 | 1.2321224165226 | | 1997 | 1.2838636585992 | | 1996 | 1.3144434461754 | | 1995 | 1.3806718697579 | | 1994 | 1.4330617299138 | | 1993 | 1.4594013206158 | | 1992 | 1.4847464493733 | | 1991 | 1.5655911311742 | | 1990 | 1.6511302922802 | | 1989 | 1.6950129908071 | | 1988 | 1.7599523397091 | | 1987 | 1.8017705532088 | | 1986 | 1.8547261743763 | | 1985 | 1.9120608299646 | | 1984 | 1.9656530421541 | | 1983 | 2.0135906820408 | | 1982 | 2.0610120643421 | | 1981 | 2.1404343212044 | | 1980 | 2.1607145389133 | | 1979 | 2.1529800373065 | | 1978 | 2.222612565936 | | 1977 | 2.270179391965 | | 1976 | 2.3522040036972 | | 1975 | 2.4936747699043 | | 1974 | 2.6098943101609 | | 1973 | 2.7083146924345 | | 1972 | 2.750318744371 | | 1971 | 2.7998326093813 | | 1970 | 2.8456292491687 | | 1969 | 2.8582071237871 | | 1968 | 2.9051224134364 | | 1967 | 2.953061632407 | | 1966 | 3.0038029392945 | | 1965 | 3.0408858996006 | | 1964 | 3.0426295425665 | | 1963 | 3.0407024587888 | | 1962 | 3.0274729636686 | | 1961 | 2.9758876539817 |
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