| Year | Value | | 2022 | 0.81152087572118 | | 2021 | 0.82246168153928 | | 2020 | 0.83590230896121 | | 2019 | 0.86528221161545 | | 2018 | 0.92488080485479 | | 2017 | 1.0001601585259 | | 2016 | 1.0754961584586 | | 2015 | 1.1409358778003 | | 2014 | 1.196115463025 | | 2013 | 1.2386268706418 | | 2012 | 1.2691040728578 | | 2011 | 1.3674436552544 | | 2010 | 1.4604183444709 | | 2009 | 1.4823230873095 | | 2008 | 1.5249550083373 | | 2007 | 1.5807534472926 | | 2006 | 1.6473108384072 | | 2005 | 1.7206665630851 | | 2004 | 1.7959744094784 | | 2003 | 1.8765839183095 | | 2002 | 1.9514983362162 | | 2001 | 2.0223789610574 | | 2000 | 2.0821635434999 | | 1999 | 2.1301893091138 | | 1998 | 2.1906027326848 | | 1997 | 2.2664435909161 | | 1996 | 2.3457484285644 | | 1995 | 2.4236760746441 | | 1994 | 2.5049519406922 | | 1993 | 2.5963470681891 | | 1992 | 2.7614878657435 | | 1991 | 2.9833649168806 | | 1990 | 3.1440362659719 | | 1989 | 3.2399991493958 | | 1988 | 3.316944578516 | | 1987 | 3.3785219459171 | | 1986 | 3.4061363143507 | | 1985 | 3.4055410835546 | | 1984 | 3.3915686555199 | | 1983 | 3.3779761209465 | | 1982 | 3.309407751393 | | 1981 | 3.2346676428313 | | 1980 | 3.2284241691411 | | 1979 | 3.2253924687219 | | 1978 | 3.2396354393756 | | 1977 | 3.2753863494551 | | 1976 | 3.3330567393145 | | 1975 | 3.4013222497 | | 1974 | 3.4607035162293 | | 1973 | 3.5361133054699 | | 1972 | 3.6953155486503 | | 1971 | 3.9143408077414 | | 1970 | 4.0800746286514 | | 1969 | 4.1860196401117 | | 1968 | 4.2736710761794 | | 1967 | 4.3712029995804 | | 1966 | 4.4595487368777 | | 1965 | 4.5423070221454 | | 1964 | 4.6006492619859 | | 1963 | 4.6230787631827 | | 1962 | 4.6639277157537 | | 1961 | 4.8206375071494 |
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