| Year | Value | | 2022 | 0.87435219852708 | | 2021 | 1.0286262278861 | | 2020 | 1.1190027896673 | | 2019 | 1.1776229891763 | | 2018 | 1.2194739081779 | | 2017 | 1.2634565676923 | | 2016 | 1.2751798040311 | | 2015 | 1.2976819115384 | | 2014 | 1.3288650608788 | | 2013 | 1.3515155546205 | | 2012 | 1.363967907838 | | 2011 | 1.3529694787544 | | 2010 | 1.3317392460537 | | 2009 | 1.3268319767911 | | 2008 | 1.3174781540768 | | 2007 | 1.3152861608293 | | 2006 | 1.348934786971 | | 2005 | 1.3761466935349 | | 2004 | 1.3957264944794 | | 2003 | 1.4169188270804 | | 2002 | 1.4428565123098 | | 2001 | 1.4684328217353 | | 2000 | 1.4910967667025 | | 1999 | 1.5301616130727 | | 1998 | 1.5754152970241 | | 1997 | 1.6119958499736 | | 1996 | 1.6425798364449 | | 1995 | 1.6694293716387 | | 1994 | 1.7076528014266 | | 1993 | 1.7462990867347 | | 1992 | 1.7871657769346 | | 1991 | 1.861646204267 | | 1990 | 1.9246743828303 | | 1989 | 1.9691046359018 | | 1988 | 2.0197118366757 | | 1987 | 2.047113929991 | | 1986 | 2.0331441543705 | | 1985 | 2.0154207154757 | | 1984 | 2.0138432600935 | | 1983 | 2.0562032868788 | | 1982 | 2.0750753333897 | | 1981 | 2.0141714149435 | | 1980 | 1.9955328027456 | | 1979 | 2.0080420158805 | | 1978 | 1.9988523075074 | | 1977 | 2.0048289508592 | | 1976 | 2.0542510159782 | | 1975 | 2.1117210321022 | | 1974 | 2.2040729714726 | | 1973 | 2.2628126117353 | | 1972 | 2.2770793143459 | | 1971 | 2.3522727143843 | | 1970 | 2.3936467152443 | | 1969 | 2.4085904008356 | | 1968 | 2.3759601680793 | | 1967 | 2.3579466895271 | | 1966 | 2.4090103584913 | | 1965 | 2.3469455065787 | | 1964 | 2.3647782403226 | | 1963 | 2.4023299373949 | | 1962 | 1.9219770330154 | | 1961 | 1.3721451835283 |
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