Year | Value | 2022 | 2.5916012677045 | 2021 | 2.5539107710944 | 2020 | 2.5840020803315 | 2019 | 2.6146547551014 | 2018 | 2.6261878034953 | 2017 | 2.6335241105812 | 2016 | 2.6425280222866 | 2015 | 2.6459571022251 | 2014 | 2.6422112603064 | 2013 | 2.896122114178 | 2012 | 3.1247890019586 | 2011 | 3.0184427605763 | 2010 | 2.8730511850203 | 2009 | 2.723800288142 | 2008 | 2.4998937601002 | 2007 | 2.3186940612337 | 2006 | 2.2604718661993 | 2005 | 2.2080345807548 | 2004 | 2.1698989980432 | 2003 | 2.1603885535254 | 2002 | 2.1449634448059 | 2001 | 2.4491651403647 | 2000 | 2.7991820841324 | 1999 | 2.7117686230807 | 1998 | 2.6307736387587 | 1997 | 2.2578178260406 | 1996 | 2.0160141081665 | 1995 | 2.7751565196712 | 1994 | 3.4327897690446 | 1993 | 4.0847344287677 | 1992 | 3.8556411355643 | 1991 | 2.9604387130315 | 1990 | 2.5745495484225 | 1989 | 2.5484124398766 | 1988 | 2.9150793967779 | 1987 | 2.9095793620895 | 1986 | 2.9200720211132 | 1985 | 2.9398329739151 | 1984 | 2.9524427141278 | 1983 | 2.9595879042424 | 1982 | 2.9617859300544 | 1981 | 2.9424879559712 | 1980 | 2.9077453391701 | 1979 | 2.8926565421156 | 1978 | 2.8867748573021 | 1977 | 2.9180166181488 | 1976 | 2.962955587526 | 1975 | 2.9676619193083 | 1974 | 2.9695846254916 | 1973 | 2.9754950072189 | 1972 | 2.9830936404786 | 1971 | 2.9988743117156 | 1970 | 3.0183700042102 | 1969 | 3.0245286936574 | 1968 | 3.0175467459097 | 1967 | 3.00019184949 | 1966 | 2.9666750486393 | 1965 | 2.9202721775608 | 1964 | 2.8707517800023 | 1963 | 2.8214207377167 | 1962 | 2.7782727783693 | 1961 | 2.7275899355721 |
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