| Year | Value | | 2022 | 1.0748367431585 | | 2021 | 1.1493184763138 | | 2020 | 1.1442097400166 | | 2019 | 1.1131724900167 | | 2018 | 1.1613784627049 | | 2017 | 1.2497240657796 | | 2016 | 1.2307953544705 | | 2015 | 1.1910611272382 | | 2014 | 1.2459602080878 | | 2013 | 1.2671572972188 | | 2012 | 1.2435712464683 | | 2011 | 1.218938691273 | | 2010 | 1.1415513368569 | | 2009 | 0.88009347559996 | | 2008 | 0.88783301709737 | | 2007 | 1.051117194237 | | 2006 | 1.2105899405382 | | 2005 | 1.517975110965 | | 2004 | 1.6611916426339 | | 2003 | 1.7465368010161 | | 2002 | 1.8580265300717 | | 2001 | 1.8992526809949 | | 2000 | 1.9055240489197 | | 1999 | 1.9150742980399 | | 1998 | 1.8761440292793 | | 1997 | 1.7877401664423 | | 1996 | 1.7533399843241 | | 1995 | 1.8666953316557 | | 1994 | 1.917797956186 | | 1993 | 1.9108212282319 | | 1992 | 1.8405331830007 | | 1991 | 1.9365440006274 | | 1990 | 2.1260590609389 | | 1989 | 2.124383168609 | | 1988 | 2.164260927052 | | 1987 | 2.2324207982693 | | 1986 | 2.3814510993569 | | 1985 | 2.5594486822631 | | 1984 | 2.6968421854847 | | 1983 | 2.7731517767492 | | 1982 | 2.7481526106241 | | 1981 | 2.6165777908841 | | 1980 | 2.4381808422093 | | 1979 | 2.347750449554 | | 1978 | 2.3647224159433 | | 1977 | 2.2751851869981 | | 1976 | 2.2237218589425 | | 1975 | 2.3740497771155 | | 1974 | 2.5026722992343 | | 1973 | 2.5598856823583 | | 1972 | 1.4093763652671 | | 1971 | 1.2277315548018 | | 1970 | 2.5111393207676 | | 1969 | 2.8821017054741 | | 1968 | 2.999688669237 | | 1967 | 3.0062455143149 | | 1966 | 2.972632953346 | | 1965 | 2.9942807397214 | | 1964 | 3.0043760138521 | | 1963 | 3.007812446014 | | 1962 | 2.9978048994162 | | 1961 | 2.9066411800282 |
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