Year | Value | 2022 | 16.380010824349 | 2021 | 16.960417318628 | 2020 | 19.154299671327 | 2019 | 19.766881537606 | 2018 | 19.603709059232 | 2017 | 19.842125113642 | 2016 | 21.087807034326 | 2015 | 22.733861419088 | 2014 | 21.679479478708 | 2013 | 22.666318153787 | 2012 | 23.468662090036 | 2011 | 21.975248999161 | 2010 | 26.42202848528 | 2009 | 24.525848295276 | 2008 | 24.305910240276 | 2007 | 27.629402139226 | 2006 | 27.736108534346 | 2005 | 25.11732990785 | 2004 | 24.438077772676 | 2003 | 23.550857169067 | 2002 | 23.12168970883 | 2001 | 22.954006883302 | 2000 | 22.501724287952 | 1999 | 22.483316264982 | 1998 | 23.394981124155 | 1997 | 25.076359770095 | 1996 | 25.318326399942 | 1995 | 24.23508735839 | 1994 | 21.519755895154 | 1993 | 21.246929282786 | 1992 | 21.817224703252 | 1991 | 22.667001557641 | 1990 | 23.665130889019 | 1989 | 23.872109558587 | 1988 | 22.825164434353 | 1987 | 17.862189087095 | 1986 | 12.134488560689 | 1985 | 9.2422133238793 | 1984 | 7.032859098102 | 1983 | 5.8885984238021 | 1982 | 2.0230288120315 | 1981 | 7.8872291227573 | 1980 | 14.047295381884 | 1979 | 12.343170776585 | 1978 | 12.016805309404 | 1977 | 10.695698476877 | 1976 | 14.422237422618 | 1975 | 7.5596011249908 |
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