| Year | Value | | 2022 | 0.3520785969046 | | 2021 | 0.49385574499437 | | 2020 | 0.11902169271715 | | 2019 | 1.0081205133252 | | 2018 | 1.749909568584 | | 2017 | 0.62939137603014 | | 2016 | 0.62488533285434 | | 2015 | 0.65383466209436 | | 2014 | 0.68700791412921 | | 2013 | 0.72111895971175 | | 2012 | 0.7267089868467 | | 2011 | 0.68713445849602 | | 2010 | 0.64770221814423 | | 2009 | 0.60043258505804 | | 2008 | 0.57184898120747 | | 2007 | 0.57513791050338 | | 2006 | 0.57130651669952 | | 2005 | 0.57892359721115 | | 2004 | 0.56168002915722 | | 2003 | 0.56188081052163 | | 2002 | 0.55108461926576 | | 2001 | 0.47656758498478 | | 2000 | 0.38657331767231 | | 1999 | 0.33899041193781 | | 1998 | 0.33331559145026 | | 1997 | 0.36000882474458 | | 1996 | 0.42819233028773 | | 1995 | 0.4927928906132 | | 1994 | 0.57171261003306 | | 1993 | 0.65687996036891 | | 1992 | 0.72435854323655 | | 1991 | 0.76343153501236 | | 1990 | 0.81721512326656 | | 1989 | 0.92585441779989 | | 1988 | 1.0654866911081 | | 1987 | 1.2314826856106 | | 1986 | 1.3728639502091 | | 1985 | 1.2613124392454 | | 1984 | 1.1438058165073 | | 1983 | 1.2139748033268 | | 1982 | 1.2561935924916 | | 1981 | 1.3074568765422 | | 1980 | 1.3876004838164 | | 1979 | 1.4252719563192 | | 1978 | 1.365880805455 | | 1977 | 1.3024350513586 | | 1976 | 1.2894476803041 | | 1975 | 1.310809731464 | | 1974 | 1.3284152513538 | | 1973 | 1.3269502223103 | | 1972 | 1.2816835419344 | | 1971 | 1.1302168553983 | | 1970 | 1.0417205589898 | | 1969 | 1.1244807880739 | | 1968 | 1.2496913149446 | | 1967 | 1.3783221765132 | | 1966 | 1.5111499863506 | | 1965 | 1.6356647790464 | | 1964 | 1.7383656503049 | | 1963 | 1.8142593661985 | | 1962 | 1.8884679424487 | | 1961 | 2.0986804298904 |
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