| Year | Value | | 2022 | 0.94915422763619 | | 2021 | 0.97811703134304 | | 2020 | 0.96440732254506 | | 2019 | 1.0645783783984 | | 2018 | 1.0760098181674 | | 2017 | 1.1383738218819 | | 2016 | 1.146424349926 | | 2015 | 1.0988986430941 | | 2014 | 1.1049796230691 | | 2013 | 1.165041143035 | | 2012 | 1.1753485756079 | | 2011 | 1.1358888923659 | | 2010 | 1.2883751769682 | | 2009 | 1.2338341891762 | | 2008 | 1.2555907411193 | | 2007 | 1.241592992916 | | 2006 | 1.2297939429697 | | 2005 | 1.1439006243482 | | 2004 | 1.4016038318718 | | 2003 | 1.3838069976001 | | 2002 | 1.3385067560334 | | 2001 | 1.2903600347566 | | 2000 | 1.3247488647241 | | 1999 | 1.4438523906064 | | 1998 | 1.3965094378674 | | 1997 | 1.3012417461069 | | 1996 | 1.2248378833825 | | 1995 | 1.2516448385188 | | 1994 | 1.3103400918897 | | 1993 | 1.3261245506114 | | 1992 | 1.5326056138361 | | 1991 | 1.5145516992046 | | 1990 | 1.4745666126807 | | 1989 | 1.3336891545687 | | 1988 | 1.2847961550284 | | 1987 | 1.2500254971953 | | 1986 | 1.2178234582829 | | 1985 | 1.3398357289528 | | 1984 | 1.7402190923318 | | 1983 | 1.8906840838776 | | 1982 | 1.9905191458027 | | 1981 | 1.8189156089958 | | 1980 | 1.5558177259991 | | 1979 | 1.6553637484587 | | 1978 | 1.6651172399545 | | 1977 | 1.7158501076086 | | 1976 | 1.7623250152161 | | 1975 | 1.7275939331265 | | 1974 | 1.6919407226959 | | 1973 | 1.7606741573034 | | 1972 | 1.762854734476 | | 1971 | 1.8426704014939 | | 1970 | 1.8721278721279 |
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