| Year | Value | | 2022 | 0.69039370989248 | | 2021 | 0.8608727231771 | | 2020 | 0.95421054444667 | | 2019 | 1.02574369597 | | 2018 | 1.0827070371329 | | 2017 | 1.1298240766232 | | 2016 | 1.1460066116921 | | 2015 | 1.1833729849606 | | 2014 | 1.2236073623107 | | 2013 | 1.2442636957438 | | 2012 | 1.2401904321519 | | 2011 | 1.2200907518626 | | 2010 | 1.2000536183238 | | 2009 | 1.1938507729534 | | 2008 | 1.1885966997178 | | 2007 | 1.1794042941423 | | 2006 | 1.2132472641374 | | 2005 | 1.2565561965172 | | 2004 | 1.281495226697 | | 2003 | 1.2933977906723 | | 2002 | 1.3337689088399 | | 2001 | 1.3918156105561 | | 2000 | 1.4190705063762 | | 1999 | 1.4459303349839 | | 1998 | 1.4997657862306 | | 1997 | 1.5365241304902 | | 1996 | 1.5631428524449 | | 1995 | 1.5989424571587 | | 1994 | 1.6376125724978 | | 1993 | 1.6624771103496 | | 1992 | 1.7283299459949 | | 1991 | 1.8433253931151 | | 1990 | 1.9527992973326 | | 1989 | 1.9435822228752 | | 1988 | 2.0027956493976 | | 1987 | 2.0283085909007 | | 1986 | 2.0140512341169 | | 1985 | 1.9885518592965 | | 1984 | 1.9864785236856 | | 1983 | 2.0352061661825 | | 1982 | 2.0742364277908 | | 1981 | 2.0369978508612 | | 1980 | 1.9970584204303 | | 1979 | 1.9720256686156 | | 1978 | 1.9645189755498 | | 1977 | 1.9812170032191 | | 1976 | 2.028758448654 | | 1975 | 2.0918045236424 | | 1974 | 2.1971119313992 | | 1973 | 2.269595699155 | | 1972 | 2.2882832096577 | | 1971 | 2.372295915274 | | 1970 | 2.4167266453978 | | 1969 | 2.429275937897 | | 1968 | 2.3891165528118 | | 1967 | 2.3707307883713 | | 1966 | 2.4378239203319 | | 1965 | 2.3705982816882 | | 1964 | 2.3875843350656 | | 1963 | 2.4328570757912 | | 1962 | 1.9120345198952 | | 1961 | 1.314382366429 |
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