Year | Value | 2023 | 2.6 | 2022 | 2.6 | 2021 | 2.828 | 2020 | 2.809 | 2019 | 2.351 | 2018 | 2.467 | 2017 | 2.822 | 2016 | 3.132 | 2015 | 3.385 | 2014 | 3.589 | 2013 | 4.038 | 2012 | 4.358 | 2011 | 4.55 | 2010 | 5.103 | 2009 | 5.068 | 2008 | 4.002 | 2007 | 3.888 | 2006 | 4.192 | 2005 | 4.446 | 2004 | 4.734 | 2003 | 5.251 | 2002 | 5.386 | 2001 | 5.02 | 2000 | 4.748 | 1999 | 4.677 | 1998 | 4.078 | 1997 | 3.374 | 1996 | 3.383 | 1995 | 3.15 | 1994 | 2.89 | 1993 | 2.539 | 1992 | 2.158 | 1991 | 2.059 | 1990 | 2.095 | 1989 | 2.3 | 1988 | 2.5 | 1987 | 2.8 | 1986 | 2.8 | 1985 | 2.6 | 1984 | 2.7 | 1983 | 2.6 | 1982 | 2.4 | 1981 | 2.2 | 1980 | 2 | 1979 | 2.1 | 1978 | 2.2 | 1977 | 2 | 1976 | 2 | 1975 | 1.9 | 1974 | 1.4 | 1973 | 1.3 | 1972 | 1.4 | 1971 | 1.2 | 1970 | 1.1 | 1969 | 1.1 | 1968 | 1.2 | 1967 | 1.3 | 1966 | 1.3 | 1965 | 1.2 | 1964 | 1.1 | 1963 | 1.3 | 1962 | 1.3 | 1961 | 1.4 | 1960 | 1.7 |
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