| Year | Value | | 2022 | 1.3133726007936 | | 2021 | 1.466768677674 | | 2020 | 1.7064706994867 | | 2019 | 1.6815257816761 | | 2018 | 1.3328467959814 | | 2017 | 0.97343306816533 | | 2016 | 0.95483129809833 | | 2015 | 0.87235347600768 | | 2014 | 0.87278421678652 | | 2013 | 0.89896796373986 | | 2012 | 0.92953605666428 | | 2011 | 0.92516575293664 | | 2010 | 0.8741794842212 | | 2009 | 0.94722744497647 | | 2008 | 0.95335427352312 | | 2007 | 0.65245791026588 | | 2006 | 0.60892231876378 | | 2005 | 0.5276636946189 | | 2004 | 0.53596996755953 | | 2003 | 0.58159629758866 | | 2002 | 0.58543103356675 | | 2001 | 0.50435894950145 | | 2000 | 0.48631976129697 | | 1999 | 0.51105152641867 | | 1998 | 0.54494782897166 | | 1997 | 0.65505482681741 | | 1996 | 0.56765662679259 | | 1995 | 0.53870924314277 | | 1994 | 0.62992060268515 | | 1993 | 0.82190641017107 | | 1992 | 1.1078382456987 | | 1991 | 0.75852456763707 | | 1990 | 0.84078508638981 | | 1989 | 0.92926299150365 | | 1988 | 0.80799067199695 | | 1987 | 0.77044635431106 | | 1986 | 0.8539333289151 | | 1985 | 0.89105984941281 | | 1984 | 1.0597317946252 | | 1983 | 1.3859892466968 | | 1982 | 1.6277206797225 | | 1981 | 1.5079424899659 | | 1977 | 0.94100125241174 | | 1976 | 0.92530781783118 |
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