| Year | Value | | 2022 | 46.017434634732 | | 2021 | 45.470684635346 | | 2020 | 43.92641665598 | | 2019 | 43.773027958978 | | 2018 | 44.485747986041 | | 2017 | 44.905047503789 | | 2016 | 44.380661438073 | | 2015 | 45.417589432034 | | 2014 | 47.615818412864 | | 2013 | 47.378391543749 | | 2012 | 48.665363405983 | | 2011 | 49.233328250646 | | 2010 | 51.326713575162 | | 2009 | 50.373042080964 | | 2008 | 51.787587383579 | | 2007 | 50.275226216186 | | 2006 | 48.260505427363 | | 2005 | 45.954784309929 | | 2004 | 45.672367332992 | | 2003 | 42.41350434646 | | 2002 | 38.883220894084 | | 2001 | 37.269297371251 | | 2000 | 35.739553532797 | | 1999 | 36.557909454954 | | 1998 | 38.347084943467 | | 1997 | 39.742242181975 | | 1996 | 38.759124188299 | | 1995 | 39.530099733357 | | 1994 | 41.696726890046 | | 1993 | 41.633008101464 | | 1992 | 40.569222269614 | | 1991 | 38.485437642301 | | 1990 | 36.687703026479 | | 1989 | 35.850534894969 | | 1988 | 37.947785338943 | | 1987 | 37.220188100316 | | 1986 | 35.2502819934 | | 1985 | 35.279013776531 | | 1984 | 34.867165830655 | | 1983 | 33.096186571565 | | 1982 | 33.737246904001 |
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