Year | Value | 2021 | 34.810154405149 | 2020 | 34.452234114448 | 2019 | 34.834042959563 | 2018 | 32.235244401329 | 2017 | 33.399879584306 | 2016 | 33.295059484392 | 2015 | 33.921619060382 | 2014 | 36.500291660969 | 2013 | 33.819752658154 | 2012 | 33.446398212041 | 2011 | 32.753489271811 | 2010 | 32.737236674584 | 2009 | 33.183839220088 | 2008 | 33.42154070903 | 2007 | 35.093001165988 | 2006 | 31.86029115887 | 2005 | 33.071767670922 | 2004 | 31.292214494564 | 2003 | 30.140777884417 | 2002 | 30.117189665558 | 2001 | 30.167195826803 | 2000 | 31.594119030262 | 1999 | 31.926570776831 | 1998 | 32.046626242937 | 1997 | 31.747026398128 | 1996 | 31.879820645853 | 1995 | 31.660832017884 | 1994 | 31.560280670166 | 1993 | 30.848082873408 | 1992 | 29.486004148959 | 1991 | 29.129390790612 | 1990 | 29.724606837575 | 1989 | 31.396660312525 | 1988 | 32.445838010958 | 1987 | 32.221692168643 | 1986 | 32.743360129723 | 1985 | 30.502808598157 | 1984 | 29.010374304974 | 1983 | 27.806520745055 | 1982 | 27.099193363892 | 1981 | 28.047752211861 | 1980 | 28.525874596727 | 1979 | 28.60343479091 | 1978 | 28.135581823056 | 1977 | 27.070720120738 | 1976 | 26.485810001564 | 1975 | 26.718374015555 | 1974 | 29.108401333987 | 1973 | 28.921772626939 | 1972 | 29.007342502153 |
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