| Year | Value | | 2022 | 0.61100555340269 | | 2021 | 0.96602484006197 | | 2020 | -1.1252426783383 | | 2019 | 0.45936258467876 | | 2018 | 2.0723701643384 | | 2017 | 3.2916338032426 | | 2016 | 3.4290789215058 | | 2015 | 3.8166049126117 | | 2014 | 3.8453793586373 | | 2013 | 2.9547571185297 | | 2012 | 1.0555629856238 | | 2011 | 0.12928111452105 | | 2010 | 2.8577456448737 | | 2009 | 6.03817950789 | | 2008 | 6.4936855776179 | | 2007 | 6.918049916211 | | 2006 | 7.3779967565212 | | 2005 | 7.8952020858036 | | 2004 | 6.8519393323519 | | 2003 | 3.9219479626771 | | 2002 | 2.4439512289901 | | 2001 | 2.6102630692956 | | 2000 | 2.7515762605179 | | 1999 | 2.8799814310671 | | 1998 | 2.9948047097839 | | 1997 | 3.0945390475272 | | 1996 | 3.1827618869051 | | 1995 | 3.2634625116082 | | 1994 | 3.3420161879426 | | 1993 | 3.4189773402231 | | 1992 | 3.4970555401393 | | 1991 | 3.4191088652043 | | 1990 | 3.3545203544577 | | 1989 | 3.4591722008857 | | 1988 | 3.5316786866563 | | 1987 | 3.5714302564935 | | 1986 | 3.5774827174077 | | 1985 | 3.5519530699378 | | 1984 | 3.5064739999249 | | 1983 | 3.4572908319346 | | 1982 | 3.5365916269934 | | 1981 | 4.0098612104975 | | 1980 | 4.4835309286767 | | 1979 | 4.6598720636842 | | 1978 | 4.8210570779423 | | 1977 | 4.9712777654778 | | 1976 | 5.1033015565025 | | 1975 | 5.2154625973662 | | 1974 | 5.3098336907212 | | 1973 | 5.3993404500566 | | 1972 | 5.1266669734441 | | 1971 | 3.7208815816592 | | 1970 | 2.6678812397579 | | 1969 | 2.7580889184315 | | 1968 | 2.8314421421095 | | 1967 | 2.9199841514126 | | 1966 | 3.064793441592 | | 1965 | 3.3854744889975 | | 1964 | 3.6546506336018 | | 1963 | 3.6986523043702 | | 1962 | 3.7550433307269 | | 1961 | 3.8330889363956 |
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