| Year | Value | | 2022 | 1.2274182379598 | | 2021 | 0.5059218392323 | | 2020 | -1.2982451305615 | | 2019 | 0.035006804519864 | | 2018 | 1.2972494870933 | | 2017 | 3.2169490405448 | | 2016 | 4.8041297854978 | | 2015 | 4.4516078884189 | | 2014 | 4.9227496816523 | | 2013 | 7.6503858174728 | | 2012 | 9.7581693038477 | | 2011 | 10.684072681914 | | 2010 | 6.6115522283317 | | 2009 | 1.7391645156995 | | 2008 | 1.7246136183463 | | 2007 | 1.7440611132888 | | 2006 | 1.7911599400701 | | 2005 | 1.8594662177695 | | 2004 | 1.5205003515989 | | 2003 | 1.1557317202492 | | 2002 | 1.2140838140905 | | 2001 | 1.2884520505263 | | 2000 | 1.3594368331046 | | 1999 | 1.4316733757508 | | 1998 | 1.5088296687357 | | 1997 | 1.5993891443673 | | 1996 | 1.7015764339221 | | 1995 | 1.8111901361092 | | 1994 | 2.9395229319693 | | 1993 | 4.2717350520749 | | 1992 | 4.641575087888 | | 1991 | 4.9020669309166 | | 1990 | 5.1561545139319 | | 1989 | 5.4192257110453 | | 1988 | 5.7087506345919 | | 1987 | 6.0422226153744 | | 1986 | 6.4495384557685 | | 1985 | 6.0921258036876 | | 1984 | 5.5447522428562 | | 1983 | 5.663234547115 | | 1982 | 5.6635841560484 | | 1981 | 5.5589667091324 | | 1980 | 5.4648738811453 | | 1979 | 5.3955810834809 | | 1978 | 5.2433935156626 | | 1977 | 4.9759259329998 | | 1976 | 4.5794102291345 | | 1975 | 4.2186205688124 | | 1974 | 3.5167750989255 | | 1973 | 2.8613116084452 | | 1972 | 2.7552342491212 | | 1971 | 2.6643802310521 | | 1970 | 2.5826672620091 | | 1969 | 2.5120378478152 | | 1968 | 2.4356840520684 | | 1967 | 2.3592889876512 | | 1966 | 2.2858689910188 | | 1965 | 2.2108249817693 | | 1964 | 2.1265309651134 | | 1963 | 2.0367715358222 | | 1962 | 1.9384757876068 | | 1961 | 1.8264656450357 |
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