| Year | Value | | 2022 | 0.62860780252607 | | 2021 | 0.55942083208543 | | 2020 | 0.727243815692 | | 2019 | 0.86026508973468 | | 2018 | 0.9516686439279 | | 2017 | 1.0804207377094 | | 2016 | 1.1332342879203 | | 2015 | 1.1670088497548 | | 2014 | 1.2414667155537 | | 2013 | 1.317160792789 | | 2012 | 1.396615461862 | | 2011 | 1.4276397653994 | | 2010 | 1.3265789572553 | | 2009 | 1.2367436923056 | | 2008 | 1.2675357417452 | | 2007 | 1.3162368191646 | | 2006 | 1.3605385738962 | | 2005 | 1.4295116710574 | | 2004 | 1.4696529746789 | | 2003 | 1.48740053113 | | 2002 | 1.5204552231802 | | 2001 | 1.5419411301452 | | 2000 | 1.5845507874618 | | 1999 | 1.640548383342 | | 1998 | 1.6857933825418 | | 1997 | 1.7281828956784 | | 1996 | 1.7812957154498 | | 1995 | 1.8568077798667 | | 1994 | 1.9044353154212 | | 1993 | 1.9288263596805 | | 1992 | 1.9503084540285 | | 1991 | 1.9763737854782 | | 1990 | 1.8359770501304 | | 1989 | 1.6864218155802 | | 1988 | 1.7111946320375 | | 1987 | 1.7286910114789 | | 1986 | 1.7901093247703 | | 1985 | 1.8635434585577 | | 1984 | 1.9363720338394 | | 1983 | 1.9946801053164 | | 1982 | 2.0345378090528 | | 1981 | 2.2325955280872 | | 1980 | 2.5918546106264 | | 1979 | 2.8425571493849 | | 1978 | 2.9459263338512 | | 1977 | 2.9500754703934 | | 1976 | 2.9557223152893 | | 1975 | 3.0200077733051 | | 1974 | 3.0627596395769 | | 1973 | 3.0980534369144 | | 1972 | 3.1219220869232 | | 1971 | 3.1481541352113 | | 1970 | 3.1817899028789 | | 1969 | 3.2209309457561 | | 1968 | 3.2609116112149 | | 1967 | 3.2874036233318 | | 1966 | 3.3193845657784 | | 1965 | 3.3405789369361 | | 1964 | 3.3250150112167 | | 1963 | 3.3024761269095 | | 1962 | 3.2686133966571 | | 1961 | 3.1784082650603 |
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