| Year | Value | | 2022 | 0.7852364193479 | | 2021 | 0.9790522575795 | | 2020 | 0.93964443580981 | | 2019 | 0.78840222782108 | | 2018 | 0.78189944416543 | | 2017 | 0.7730058012683 | | 2016 | 0.75450838069992 | | 2015 | 0.7143137221497 | | 2014 | 0.67249641197474 | | 2013 | 0.61665941951873 | | 2012 | 0.54790455609365 | | 2011 | 0.49435753389304 | | 2010 | 0.45872016271975 | | 2009 | 0.45918251863985 | | 2008 | 0.53931400092225 | | 2007 | 0.5803666400252 | | 2006 | 0.54419029535905 | | 2005 | 0.57278008442795 | | 2004 | 0.65585548954034 | | 2003 | 0.7573014274997 | | 2002 | 0.8998222939507 | | 2001 | 1.0521881026019 | | 2000 | 1.1836929876101 | | 1999 | 1.3058566769301 | | 1998 | 1.4453939508349 | | 1997 | 1.7458893480351 | | 1996 | 2.0771206926155 | | 1995 | 0.017196994762699 | | 1994 | 0.02999179966986 | | 1993 | 3.011593411951 | | 1992 | 3.9074285131028 | | 1991 | 4.0953740584567 | | 1990 | 3.3407413815376 | | 1989 | 3.8906749040035 | | 1988 | 4.6064329267707 | | 1987 | 3.8315589658079 | | 1986 | 3.8746950165574 | | 1985 | 3.638430675802 | | 1984 | 3.2712804623158 | | 1983 | 3.2664787098789 | | 1982 | 2.9153329312811 | | 1981 | 2.9054361245462 | | 1980 | 3.3073820528968 | | 1979 | 3.3101509229154 | | 1978 | 3.248713907237 | | 1977 | 3.1602624314755 | | 1976 | 3.0769815035197 | | 1975 | 2.9700667132314 | | 1974 | 2.8621074871867 | | 1973 | 2.7751786249531 | | 1972 | 2.73188249715 | | 1971 | 2.6841208680988 | | 1970 | 2.6308065513321 | | 1969 | 2.5814505290438 | | 1968 | 2.5868569532653 | | 1967 | 2.6660857592312 | | 1966 | 2.6790968905993 | | 1965 | 2.55240445919 | | 1964 | 2.4074162332217 | | 1963 | 2.3151964084435 | | 1962 | 2.26859447687 | | 1961 | 2.2653095501734 |
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