| Year | Value | | 2022 | 0.77260715738691 | | 2021 | 0.87369484676633 | | 2020 | 0.88412714508891 | | 2019 | 0.75035965749035 | | 2018 | 0.74502803964834 | | 2017 | 0.7572790337021 | | 2016 | 0.72973769179349 | | 2015 | 0.69811641313399 | | 2014 | 0.74778009537978 | | 2013 | 0.75082538308457 | | 2012 | 0.77846425064704 | | 2011 | 0.79089755845203 | | 2010 | 0.82123271153062 | | 2009 | 0.83337956469292 | | 2008 | 0.87070512307059 | | 2007 | 0.90045717278703 | | 2006 | 0.7858132444592 | | 2005 | 0.85014257402626 | | 2004 | 0.89348046624293 | | 2003 | 0.91364031878926 | | 2002 | 0.88352783657309 | | 2001 | 0.90824004070951 | | 2000 | 0.98031858008593 | | 1999 | 0.98024612338221 | | 1998 | 1.018072862998 | | 1997 | 1.0464339818971 | | 1996 | 1.0496829774227 | | 1995 | 1.0732320520695 | | 1994 | 1.094453076227 | | 1993 | 1.1155845413425 | | 1992 | 1.0992140715867 | | 1991 | 1.1542171184724 | | 1990 | 1.1956602667056 | | 1989 | 1.2341549252625 | | 1988 | 1.2991811442018 | | 1987 | 1.4166779027451 | | 1986 | 1.5087585414904 | | 1985 | 1.5126235665005 | | 1984 | 1.4141583361715 | | 1983 | 1.3911758841648 | | 1982 | 1.4129967301836 | | 1981 | 1.3800517334901 | | 1980 | 1.4202461061149 | | 1979 | 1.4338457316943 | | 1978 | 1.4292126118907 | | 1977 | 1.3459518906219 | | 1976 | 1.3651968107706 | | 1975 | 1.4512783637139 | | 1974 | 1.2768825193592 | | 1973 | 1.1849885730058 | | 1972 | 1.2022866645814 | | 1971 | 1.2461069539107 | | 1970 | 1.3801301213153 | | 1969 | 1.4992565671642 | | 1968 | 1.5426747490549 | | 1967 | 1.6091664157418 | | 1966 | 1.6244051316426 | | 1965 | 1.5072133874239 | | 1964 | 1.8873002425579 | | 1963 | 1.579667758382 | | 1962 | 1.3520718589647 | | 1961 | 1.3093375230276 | | 1960 | 1.4581856994971 |
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