| Year | Value | | 2022 | 0.30501524671998 | | 2021 | 0.28550861863843 | | 2020 | 0.27135050766999 | | 2019 | 0.34137414315751 | | 2018 | 0.35849458181616 | | 2017 | 0.29020211635109 | | 2016 | 0.26386878856537 | | 2015 | 0.3555692400583 | | 2014 | 0.46824634207038 | | 2013 | 0.51653966130755 | | 2012 | 0.48395348976888 | | 2011 | 0.48269478175835 | | 2010 | 0.49282112569031 | | 2009 | 0.51310287617849 | | 2008 | 0.55756375763196 | | 2007 | 0.61649393244632 | | 2006 | 0.69370661211418 | | 2005 | 0.74991832502453 | | 2004 | 0.73509806756324 | | 2003 | 0.71044808965297 | | 2002 | 0.72874620687397 | | 2001 | 0.72943078950882 | | 2000 | 0.68678258685703 | | 1999 | 0.51638425192185 | | 1998 | 0.3709074320473 | | 1997 | 0.35649796330582 | | 1996 | 0.35687155629296 | | 1995 | 0.36354332756236 | | 1994 | 0.3739124296966 | | 1993 | 0.43443854695007 | | 1992 | 0.498037271076 | | 1991 | 0.87970718299907 | | 1990 | 0.48081715425196 | | 1989 | 0.50960491878075 | | 1988 | 0.53077442630459 | | 1987 | 0.53180239735572 | | 1986 | 0.52188525375023 | | 1985 | 0.52017356953579 | | 1984 | 0.50423041230995 | | 1983 | 0.53462148199141 | | 1982 | 0.58175388253742 | | 1981 | 0.57680207483332 | | 1980 | 0.54461015158889 | | 1979 | 0.48952965381755 | | 1978 | 0.48608579948771 | | 1977 | 0.47219504106493 | | 1976 | 0.46586203042874 | | 1975 | 0.56096524003926 | | 1974 | 0.67924315225146 | | 1973 | 0.78676895660007 | | 1972 | 0.86368132726516 | | 1971 | 0.88752182552335 | | 1970 | 0.87660178795993 | | 1969 | 0.89267773827798 | | 1968 | 0.9550306341736 | | 1967 | 1.0323917247214 | | 1966 | 1.0782871266231 | | 1965 | 1.1197366100284 | | 1964 | 1.1226612057238 | | 1963 | 1.0642604497184 | | 1962 | 1.0926788830025 | | 1961 | 1.0909509053906 |
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