Year | Value | 2023 | 29.905 | 2022 | 30.081 | 2021 | 30.243 | 2020 | 30.392 | 2019 | 30.527 | 2018 | 30.648 | 2017 | 30.754 | 2016 | 30.846 | 2015 | 30.939 | 2014 | 31.032 | 2013 | 31.125 | 2012 | 31.218 | 2011 | 31.311 | 2010 | 31.404 | 2009 | 31.498 | 2008 | 31.675 | 2007 | 31.853 | 2006 | 32.031 | 2005 | 32.21 | 2004 | 32.403 | 2003 | 32.573 | 2002 | 32.717 | 2001 | 32.817 | 2000 | 32.855 | 1999 | 32.894 | 1998 | 32.933 | 1997 | 32.971 | 1996 | 33.01 | 1995 | 33.049 | 1994 | 33.088 | 1993 | 33.126 | 1992 | 33.165 | 1991 | 33.204 | 1990 | 33.243 | 1989 | 33.282 | 1988 | 33.601 | 1987 | 34.17 | 1986 | 34.742 | 1985 | 35.319 | 1984 | 35.9 | 1983 | 36.496 | 1982 | 37.096 | 1981 | 37.7 | 1980 | 38.307 | 1979 | 38.919 | 1978 | 39.566 | 1977 | 40.244 | 1976 | 40.925 | 1975 | 41.611 | 1974 | 42.3 |
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