| Year | Value | | 2022 | 0.73501594210517 | | 2021 | 0.72755639399722 | | 2020 | 0.70949830239332 | | 2019 | 0.78525898208049 | | 2018 | 0.76771771837025 | | 2017 | 0.74174490387825 | | 2016 | 0.67766120277703 | | 2015 | 0.69576243386048 | | 2014 | 0.7848271726157 | | 2013 | 0.82116378549536 | | 2012 | 0.86940322566929 | | 2011 | 0.72939379047123 | | 2010 | 0.7011103983744 | | 2009 | 0.77100950345844 | | 2008 | 0.71154500716418 | | 2007 | 0.74530249763352 | | 2006 | 0.82312097730267 | | 2005 | 0.87950293354178 | | 2004 | 0.87848295557328 | | 2003 | 0.90704239671527 | | 2002 | 0.94530218306467 | | 2001 | 1.0541948777565 | | 2000 | 1.2522824792737 | | 1999 | 1.3116459937343 | | 1998 | 1.3133397029292 | | 1997 | 1.372294024939 | | 1996 | 1.4367001101544 | | 1995 | 1.4445039795699 | | 1994 | 1.4390165451309 | | 1993 | 1.4465038346161 | | 1992 | 1.4060045401014 | | 1991 | 1.391284762105 | | 1990 | 1.428545703939 | | 1989 | 1.4671405771336 | | 1988 | 1.4490395199597 | | 1987 | 1.4003629143521 | | 1986 | 1.3866453828489 | | 1985 | 1.3720730238744 | | 1984 | 1.3911610733001 | | 1983 | 1.4146803649013 | | 1982 | 1.3441958052292 | | 1981 | 1.3625108991096 | | 1980 | 1.5599179649036 | | 1979 | 1.6837414628083 | | 1978 | 1.6747600237747 | | 1977 | 1.6392073764326 | | 1976 | 1.6621835556991 | | 1975 | 1.7167803622366 | | 1974 | 1.7242958787698 | | 1973 | 1.7133951930128 | | 1972 | 1.6409679121089 | | 1971 | 2.0091742841687 | | 1970 | 2.5501417938897 | | 1969 | 2.6968037231304 | | 1968 | 2.7561398052286 | | 1967 | 2.6547467847713 | | 1966 | 2.4402524375149 | | 1965 | 2.4181932198992 | | 1964 | 2.4270451186955 | | 1963 | 2.318877937557 | | 1962 | 2.2728918533378 | | 1961 | 2.1738681063896 |
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