| Year | Value | | 2022 | 0.63655511514644 | | 2021 | 0.69471768831976 | | 2020 | 0.84038926812805 | | 2019 | 0.93768927363529 | | 2018 | 0.96620643586614 | | 2017 | 1.0064395244609 | | 2016 | 1.0589420586891 | | 2015 | 1.1108549322781 | | 2014 | 1.1595066418027 | | 2013 | 1.2128178098783 | | 2012 | 1.2559414583581 | | 2011 | 1.2557380886131 | | 2010 | 1.2515172914041 | | 2009 | 1.2715320899429 | | 2008 | 1.302170535079 | | 2007 | 1.3118475961457 | | 2006 | 1.2993088987366 | | 2005 | 1.2607482956029 | | 2004 | 1.2732264886851 | | 2003 | 1.3380438913487 | | 2002 | 1.3735192806087 | | 2001 | 1.4100988547982 | | 2000 | 1.447088484089 | | 1999 | 1.5000429434582 | | 1998 | 1.5649328627064 | | 1997 | 1.6030893002704 | | 1996 | 1.6188168606457 | | 1995 | 1.6341675197014 | | 1994 | 1.650685577144 | | 1993 | 1.6718280096341 | | 1992 | 1.7101353035243 | | 1991 | 1.7421774992587 | | 1990 | 1.7782908668732 | | 1989 | 1.8354293362587 | | 1988 | 1.880610556526 | | 1987 | 1.924259575814 | | 1986 | 1.9966681756408 | | 1985 | 2.1088758204319 | | 1984 | 2.2056964360231 | | 1983 | 2.2687179615083 | | 1982 | 2.3084426386151 | | 1981 | 2.3406663368734 | | 1980 | 2.3793295220094 | | 1979 | 2.4076663007879 | | 1978 | 2.4288346633972 | | 1977 | 2.4529341620207 | | 1976 | 2.489691100482 | | 1975 | 2.5221579538466 | | 1974 | 2.5618527604607 | | 1973 | 2.6035110954922 | | 1972 | 2.63262496161 | | 1971 | 2.6705934222838 | | 1970 | 2.7085655781128 | | 1969 | 2.7210776683407 | | 1968 | 2.6723791375248 | | 1967 | 2.5734144776984 | | 1966 | 2.3479478913574 | | 1965 | 2.4850106315999 | | 1964 | 2.7874468225867 | | 1963 | 2.7650226207429 | | 1962 | 2.7461735245754 | | 1961 | 2.7167513016584 |
|