Year | Value | 2022 | 21.149135889573 | 2021 | 24.251702529123 | 2020 | 21.58867979379 | 2019 | 21.492287078098 | 2018 | 21.128837544065 | 2017 | 20.684695137636 | 2016 | 20.198332850253 | 2015 | 18.531728968097 | 2014 | 18.860548523118 | 2013 | 18.031821822677 | 2012 | 17.550877711009 | 2011 | 17.64425638649 | 2010 | 17.272553270356 | 2009 | 17.628248898372 | 2008 | 18.992237289284 | 2007 | 20.875273464756 | 2006 | 20.488067225274 | 2005 | 20.279483510625 | 2004 | 20.7760312926 | 2003 | 20.399281035494 | 2002 | 21.066692557237 | 2001 | 20.996831509012 | 2000 | 20.589781624222 | 1999 | 21.030905545072 | 1998 | 21.629638129286 | 1997 | 22.421969308089 | 1996 | 22.368040471279 | 1995 | 22.10102603027 | 1994 | 20.076807305689 | 1993 | 19.982953951602 | 1992 | 19.259049524525 | 1991 | 20.25976542183 | 1990 | 21.107473021601 | 1989 | 21.2747258072 | 1988 | 21.983218135528 | 1987 | 21.921902570519 | 1986 | 22.086122715383 | 1985 | 22.471452459783 | 1984 | 22.865127224372 | 1983 | 22.776099233869 | 1982 | 22.194270721984 | 1981 | 22.507485434263 | 1980 | 24.757248898602 | 1979 | 26.141148831596 | 1978 | 26.055073932572 | 1977 | 25.627651717444 | 1976 | 25.626718940098 | 1975 | 24.056013031205 | 1974 | 25.735018203369 | 1973 | 24.980155613313 | 1972 | 24.780307436701 | 1971 | 25.493826264003 | 1970 | 27.077111336956 |
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