Year | Value | 2021 | 29.405715826368 | 2020 | 29.308438932327 | 2019 | 29.428417363171 | 2018 | 29.563224588838 | 2017 | 29.722072315165 | 2016 | 29.856988667026 | 2015 | 29.991905018888 | 2014 | 30.12682137075 | 2013 | 30.172181867097 | 2012 | 30.306698950767 | 2011 | 30.441216034436 | 2010 | 30.4868173258 | 2009 | 30.018832391714 | 2008 | 29.986548291633 | 2007 | 30.021522733387 | 2006 | 29.921980091472 | 2005 | 29.997309658327 | 2004 | 30.032284100081 | 2003 | 30.067258541835 | 2002 | 30.102232983589 | 2001 | 30.137207425343 | 2000 | 29.997309658327 | 1999 | 29.015334947538 | 1998 | 28.907721280603 | 1997 | 28.7866559053 | 1996 | 28.679042238364 | 1995 | 28.679042238364 | 1994 | 28.719397363465 | 1993 | 28.92117298897 | 1992 | 28.92117298897 | 1991 | 28.705945655098 | 1990 | 28.571428571429 | 1989 | 28.248587570621 | 1988 | 27.845036319613 | 1987 | 27.508743610439 | 1986 | 27.172450901265 | 1985 | 26.83615819209 | 1984 | 26.446058649448 | 1983 | 26.109765940274 | 1982 | 25.746569814366 | 1981 | 25.316115146624 | 1980 | 24.952919020716 | 1979 | 24.912563895615 | 1978 | 24.885660478881 | 1977 | 24.872208770514 | 1976 | 24.576271186441 | 1975 | 24.293785310734 | 1974 | 24.011299435028 | 1973 | 23.715361850955 | 1972 | 23.446327683616 | 1971 | 23.042776432607 | 1970 | 22.652676889965 | 1969 | 22.693032015066 | 1968 | 22.58541834813 | 1967 | 22.450901264461 | 1966 | 22.437449556094 | 1965 | 22.302932472424 | 1964 | 22.168415388754 | 1963 | 22.114608555287 | 1962 | 21.980091471617 | 1961 | 21.845574387947 |
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