Year | Value | 2022 | 8.9 | 2021 | 10.5 | 2020 | 9.9 | 2019 | 10.2 | 2018 | 10.4 | 2017 | 10.6 | 2016 | 10.9 | 2015 | 10.8 | 2014 | 11.5 | 2013 | 12 | 2012 | 12.9 | 2011 | 13.5 | 2010 | 14.7 | 2009 | 16.2 | 2008 | 16.8 | 2007 | 18 | 2006 | 19.6 | 2005 | 22.5 | 2004 | 24.1 | 2003 | 25.7 | 2002 | 26.4 | 2001 | 26.9 | 2000 | 27.1 | 1999 | 29.1 | 1998 | 28.6 | 1997 | 29.1 | 1996 | 29.7 | 1995 | 28.6 | 1994 | 28.8 | 1993 | 30.5 | 1992 | 30.3 | 1991 | 30.5 | 1990 | 31.3 | 1989 | 29.4 | 1988 | 30.4 | 1987 | 29.8 | 1986 | 26.4 | 1985 | 33.1 | 1984 | 35 | 1983 | 35.4 | 1982 | 31.5 | 1981 | 30.8 |
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