Year | Value | 2021 | 42.308431915429 | 2020 | 42.308431915429 | 2019 | 42.308431915429 | 2018 | 42.303397936068 | 2017 | 42.09197080292 | 2016 | 42.119657689404 | 2015 | 42.633123584193 | 2014 | 42.117140699723 | 2013 | 41.666599546942 | 2012 | 41.354492826579 | 2011 | 40.755449282658 | 2010 | 40.385451799648 | 2009 | 40.078379058646 | 2008 | 39.824163100931 | 2007 | 39.580015101938 | 2006 | 39.353486030707 | 2005 | 39.126956959477 | 2004 | 38.900427888246 | 2003 | 38.673898817015 | 2002 | 38.49267556003 | 2001 | 38.220840674553 | 2000 | 37.994311603322 | 1999 | 37.810571356657 | 1998 | 37.556355398943 | 1997 | 36.924590989177 | 1996 | 36.924590989177 | 1995 | 36.924590989177 | 1994 | 36.547042537126 | 1993 | 36.169494085074 | 1992 | 36.169494085074 | 1991 | 35.791945633023 | 1990 | 35.589151774478 | 1989 | 35.383840926252 | 1988 | 35.084319154291 | 1987 | 34.784797382331 | 1986 | 34.48527561037 | 1985 | 34.160583941606 | 1984 | 33.861062169645 | 1983 | 33.561540397684 | 1982 | 33.262018625724 | 1981 | 32.965013843443 | 1980 | 32.451547948653 | 1979 | 31.943116033224 | 1978 | 31.459854014598 | 1977 | 30.948905109489 | 1976 | 30.465643090863 | 1975 | 29.957211175434 | 1974 | 29.446262270325 | 1973 | 28.947898313617 | 1972 | 28.744022149509 | 1971 | 28.537628995721 | 1970 | 28.328718852253 | 1969 | 28.122325698465 | 1968 | 27.915932544677 | 1967 | 27.71960734961 | 1966 | 27.510697206142 | 1965 | 27.241379310345 | 1964 | 26.977095393909 | 1963 | 26.69015857035 | 1962 | 26.438459602316 | 1961 | 26.204379562044 |
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