Year | Value | 2021 | 2.293 | 2020 | 2.323 | 2019 | 2.408 | 2018 | 2.501 | 2017 | 2.479 | 2016 | 2.625 | 2015 | 2.427 | 2014 | 2.563 | 2013 | 2.537 | 2012 | 2.572 | 2011 | 2.311 | 2010 | 2.514 | 2009 | 2.375 | 2008 | 2.579 | 2007 | 2.566 | 2006 | 2.503 | 2005 | 2.637 | 2004 | 2.592 | 2003 | 2.54 | 2002 | 2.559 | 2001 | 2.336 | 2000 | 2.582 | 1999 | 2.325 | 1998 | 2.336 | 1997 | 2.514 | 1996 | 2.584 | 1995 | 2.456 | 1994 | 2.392 | 1993 | 2.509 | 1992 | 2.524 | 1991 | 2.628 | 1990 | 2.798 | 1989 | 2.706 | 1988 | 2.572 | 1987 | 2.362 | 1986 | 2.41 | 1985 | 2.281 | 1984 | 2.167 | 1983 | 2.161 | 1982 | 2.348 | 1981 | 2.467 | 1980 | 2.463 | 1979 | 2.696 | 1978 | 2.597 | 1977 | 2.684 | 1976 | 2.738 | 1975 | 2.902 | 1974 | 3.065 | 1973 | 3.22 | 1972 | 3.256 | 1971 | 3.215 | 1970 | 3.418 |
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