| Year | Value | | 2022 | 1.320394102095 | | 2021 | 1.223435722582 | | 2020 | 1.4000724003939 | | 2019 | 1.1800096207451 | | 2018 | 1.1322072788533 | | 2017 | 1.044469400792 | | 2016 | 1.0235029512517 | | 2015 | 1.0568199660043 | | 2014 | 1.0352548767409 | | 2013 | 1.0799892319389 | | 2012 | 1.0488096267912 | | 2011 | 1.0880614954412 | | 2010 | 1.0895537274663 | | 2009 | 1.0788782114688 | | 2008 | 0.96181183148724 | | 2007 | 0.97344482490044 | | 2006 | 0.88813110590135 | | 2005 | 0.90420465369438 | | 2004 | 0.81021443104477 | | 2003 | 0.84138128488891 | | 2002 | 1.1302387299052 | | 2001 | 1.090670038634 | | 2000 | 0.84033103810209 | | 1999 | 0.92054923959354 | | 1998 | 0.92294290793597 | | 1997 | 1.0077662062942 | | 1996 | 1.0744091527952 | | 1995 | 1.1750583278587 | | 1994 | 1.3522211794245 | | 1993 | 1.6787287901422 | | 1992 | 2.2535767822863 | | 1991 | 2.7325774545679 | | 1990 | 3.4136659874494 | | 1989 | 4.8723458498269 | | 1988 | 4.271323885069 | | 1987 | 4.4691639512447 | | 1986 | 4.3299567180393 | | 1985 | 6.5897161146428 | | 1984 | 6.4432824370681 | | 1983 | 3.5514498936271 | | 1982 | 2.7763365312517 | | 1981 | 2.2795464155422 | | 1980 | 1.7363364875446 | | 1979 | 1.5776536243051 | | 1978 | 1.1185260125879 | | 1977 | 0.97184222556561 | | 1976 | 0.88184719561741 | | 1975 | 0.83073793835468 | | 1974 | 0.80139747669085 | | 1973 | 0.86497061180001 | | 1972 | 0.88157282464819 | | 1971 | 0.71802040517766 | | 1970 | 0.62983405838319 | | 1969 | 0.71546150132435 | | 1968 | 0.65557118319907 | | 1967 | 0.69425398268614 | | 1966 | 0.70907983568408 | | 1965 | 0.7386838966954 |
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