| Year | Value | | 2022 | 0.37819863380304 | | 2021 | 0.5810676434653 | | 2020 | 0.70687580551608 | | 2019 | 0.80034438175814 | | 2018 | 0.86895632499866 | | 2017 | 0.93964803038654 | | 2016 | 0.9724345493904 | | 2015 | 1.0195476051116 | | 2014 | 1.0640881396106 | | 2013 | 1.084404103733 | | 2012 | 1.0688299470508 | | 2011 | 1.0257964699547 | | 2010 | 0.9980999380125 | | 2009 | 1.0138526093096 | | 2008 | 1.006816585843 | | 2007 | 0.9929139364383 | | 2006 | 1.0373571211151 | | 2005 | 1.0788950082496 | | 2004 | 1.100440586501 | | 2003 | 1.1132235346133 | | 2002 | 1.1400877042398 | | 2001 | 1.1824377611691 | | 2000 | 1.2181930845761 | | 1999 | 1.2778948995814 | | 1998 | 1.337056092449 | | 1997 | 1.3760173427522 | | 1996 | 1.4009663447402 | | 1995 | 1.4330429995723 | | 1994 | 1.4694886613835 | | 1993 | 1.506142976289 | | 1992 | 1.5747349556193 | | 1991 | 1.6798669840863 | | 1990 | 1.7473973975569 | | 1989 | 1.7947099079512 | | 1988 | 1.8557896563244 | | 1987 | 1.880491847385 | | 1986 | 1.8599651185768 | | 1985 | 1.8339037686737 | | 1984 | 1.8365565875696 | | 1983 | 1.8767829046245 | | 1982 | 1.9022240724678 | | 1981 | 1.8499343069035 | | 1980 | 1.8222243137677 | | 1979 | 1.8275917706721 | | 1978 | 1.8348526329516 | | 1977 | 1.8688262120363 | | 1976 | 1.9355652057652 | | 1975 | 1.9960263542834 | | 1974 | 2.1023290107998 | | 1973 | 2.1819690186124 | | 1972 | 2.2413809131617 | | 1971 | 2.3389008170451 | | 1970 | 2.3462741804345 | | 1969 | 2.3508528475338 | | 1968 | 2.3100915228298 | | 1967 | 2.29443844524 | | 1966 | 2.3610702283142 | | 1965 | 2.2878234321776 | | 1964 | 2.3165443377049 | | 1963 | 2.3693999526686 | | 1962 | 1.794551073196 | | 1961 | 1.1392806359093 |
|