Year | Value | 2022 | 2.5486157249738 | 2021 | 2.3849106564496 | 2020 | 2.4990686171573 | 2019 | 2.308597075651 | 2018 | 2.2172410830983 | 2017 | 2.2122672154677 | 2016 | 2.2511759366173 | 2015 | 2.2766332351728 | 2014 | 2.2754556498551 | 2013 | 2.382930055977 | 2012 | 2.5291168991923 | 2011 | 2.615926461046 | 2010 | 2.7130632228856 | 2009 | 2.7519282660323 | 2008 | 2.5153581976189 | 2007 | 2.4154316746315 | 2006 | 2.4466854717209 | 2005 | 2.4546485205333 | 2004 | 2.4407755271117 | 2003 | 2.4166073295906 | 2002 | 2.3170613371532 | 2001 | 2.1769637585974 | 2000 | 2.1417417936102 | 1999 | 2.1414093860784 | 1998 | 2.2033789543704 | 1997 | 2.2508385041949 | 1996 | 2.2635918395634 | 1995 | 2.3253893198264 | 1994 | 2.5487569387962 | 1993 | 2.733315314575 | 1992 | 2.8928333376587 | 1991 | 2.9445964692932 | 1990 | 3.2838082947753 | 1989 | 3.4399194688862 | 1988 | 3.499942777884 | 1987 | 3.7597676256649 | 1986 | 3.9970917094893 | 1985 | 4.2561787884828 | 1984 | 4.1467823276243 | 1983 | 4.1233338762947 | 1982 | 4.2810608634414 | 1981 | 3.7087902269098 | 1980 | 3.4385624763611 | 1979 | 3.3622860190472 | 1978 | 3.359374051184 | 1977 | 3.5333057068749 | 1976 | 3.5786016439056 | 1975 | 3.782445561727 | 1974 | 3.8867633890023 | 1973 | 3.8854398962732 | 1972 | 4.3649145459486 | 1971 | 4.6666871216865 | 1970 | 5.2385958479597 | 1969 | 5.972671878365 | 1968 | 6.4844639052047 | 1967 | 6.6207598531196 | 1966 | 6.1604955890413 | 1965 | 5.7442321635327 | 1964 | 6.0590368484453 | 1963 | 6.5960507582349 | 1962 | 7.0227181651395 | 1961 | 6.9513027752273 | 1960 | 6.9858524352074 |
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