| Year | Value | | 2022 | 0.65100396950111 | | 2021 | 0.69213217672224 | | 2020 | 0.6731538963755 | | 2019 | 0.54534303767569 | | 2018 | 0.53210217428731 | | 2017 | 0.50622228976756 | | 2016 | 0.50138704417578 | | 2015 | 0.5204692411951 | | 2014 | 0.55639126088479 | | 2013 | 0.57855993183973 | | 2012 | 0.59276495772063 | | 2011 | 0.62319102633648 | | 2010 | 0.57021468727248 | | 2009 | 0.73813295344609 | | 2008 | 0.96289209284099 | | 2007 | 0.96118151331312 | | 2006 | 0.97743120513063 | | 2005 | 1.0719415485473 | | 2004 | 1.2482266720781 | | 2003 | 1.3247573245213 | | 2002 | 1.3131615737967 | | 2001 | 1.4358476024528 | | 2000 | 1.2175139090008 | | 1999 | 1.2102292165583 | | 1998 | 1.348927492076 | | 1997 | 1.4819123594261 | | 1996 | 1.2376344417393 | | 1995 | 0.85988796972957 | | 1994 | 0.92647348708851 | | 1993 | 1.1223240168039 | | 1992 | 0.76992186801595 | | 1991 | 1.2963490577557 | | 1990 | 1.2315110445038 | | 1989 | 1.2108653318021 | | 1988 | 1.3471834264432 | | 1987 | 1.4290401370712 | | 1986 | 1.551935381404 | | 1985 | 1.780054933446 | | 1984 | 1.8731563421829 | | 1981 | 2.97845373891 | | 1980 | 2.7689185271093 | | 1979 | 2.9272391194757 | | 1978 | 2.4198520345253 | | 1977 | 2.3071993163854 | | 1976 | 1.880209573708 | | 1975 | 1.6371457489879 | | 1974 | 1.6706891928131 | | 1973 | 1.5238575268817 | | 1972 | 1.4881933003844 | | 1971 | 1.316573556797 | | 1970 | 1.3512429831596 | | 1969 | 1.5072463768116 | | 1968 | 1.546218487395 | | 1967 | 1.5500259201659 | | 1966 | 1.5422748554117 | | 1965 | 1.5908543922984 | | 1964 | 1.45875 | | 1963 | 1.4603698811096 | | 1962 | 1.5373134328358 | | 1961 | 1.5021520803443 |
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