| Year | Value | | 2022 | 1.092190045588 | | 2021 | 1.0794434996739 | | 2020 | 1.0543763378626 | | 2019 | 1.0223653969168 | | 2018 | 1.0578570440987 | | 2017 | 1.055796282354 | | 2016 | 1.0936919337699 | | 2015 | 1.0913698672299 | | 2014 | 1.0157610032095 | | 2013 | 0.97236260326442 | | 2012 | 0.91379934806313 | | 2011 | 0.90315074730673 | | 2010 | 0.89602408427544 | | 2009 | 0.75719306630447 | | 2008 | 0.69827898971524 | | 2007 | 0.76206456933502 | | 2006 | 0.79212401073068 | | 2005 | 0.82394130016329 | | 2004 | 0.9946145725831 | | 2003 | 1.0743069684707 | | 2002 | 1.3025984565285 | | 2001 | 1.451604643992 | | 2000 | 1.4872640120632 | | 1999 | 1.4876626596672 | | 1998 | 1.6019715468314 | | 1997 | 1.5435445395517 | | 1996 | 1.5553502988608 | | 1995 | 1.627214037411 | | 1994 | 1.2941140647361 | | 1993 | 1.3792783708288 | | 1992 | 2.1060392591998 | | 1991 | 2.1817780109917 | | 1990 | 2.0464840801596 | | 1989 | 2.3826354788624 | | 1988 | 2.4475441624245 | | 1987 | 3.1518789872711 | | 1986 | 5.7446206306312 | | 1985 | 5.3870763637012 | | 1984 | 5.2475641746299 | | 1983 | 5.4143194886314 | | 1982 | 5.4976020152761 | | 1981 | 5.5842939187813 | | 1980 | 4.5206325086661 | | 1979 | 8.5026045255354 | | 1978 | 10.109111256178 | | 1977 | 5.4766523486213 | | 1976 | 4.6889717023629 | | 1975 | 5.3600547051707 | | 1974 | 5.3551331749406 | | 1973 | 4.1746165000382 | | 1972 | 3.4326888650197 | | 1971 | 3.0976156511107 | | 1970 | 2.2999781992588 | | 1969 | 1.7349776326925 | | 1968 | 1.4732029464059 | | 1967 | 1.4231240637342 |
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