Year | Value | 2022 | 19.05466193119 | 2021 | 19.489779003213 | 2020 | 17.691440054819 | 2019 | 18.392278426655 | 2018 | 18.33232283553 | 2017 | 18.021004316724 | 2016 | 16.325906100033 | 2015 | 15.644796258525 | 2014 | 14.965766333755 | 2013 | 15.618796573276 | 2012 | 13.790994245321 | 2011 | 13.331253298715 | 2010 | 10.614950588091 | 2009 | 11.018898652647 | 2008 | 11.425002985602 | 2007 | 13.432538076846 | 2006 | 12.782193783985 | 2005 | 13.693737976772 | 2004 | 15.531097102641 | 2003 | 16.41342882886 | 2002 | 17.363764807092 | 2001 | 18.121892798303 | 2000 | 17.94589936085 | 1999 | 20.294427791567 | 1998 | 22.156802147133 | 1997 | 21.627857263511 | 1996 | 21.490152643697 | 1995 | 24.634302879129 | 1994 | 21.655323638358 | 1993 | 22.768146972823 | 1992 | 25.29432664618 | 1991 | 25.239750342778 | 1990 | 28.003186867678 | 1989 | 29.273694646417 | 1988 | 28.89346398043 | 1987 | 28.646284633728 | 1986 | 26.354285802201 | 1985 | 22.150399700289 | 1984 | 19.484651431118 | 1983 | 20.937951778326 | 1982 | 21.478549546803 | 1981 | 23.072616285902 | 1980 | 27.376491571537 | 1979 | 28.599979939326 | 1978 | 25.978886850485 | 1977 | 21.077120765455 | 1976 | 18.077838947002 | 1975 | 16.24996946613 |
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