| Year | Value | | 2022 | 4.3935966591265 | | 2021 | 1.5102004769054 | | 2020 | 0.61441235846577 | | 2019 | 0.84978312826417 | | 2018 | 0.79407566024272 | | 2017 | 0.25941497450575 | | 2016 | 0.55155235299356 | | 2015 | 0.60129100716239 | | 2014 | 0.47978676143932 | | 2013 | 1.5702553921126 | | 2012 | 1.6792071939806 | | 2011 | 3.484949197607 | | 2010 | 2.6913700633838 | | 2009 | 3.3561781898811 | | 2008 | 4.5521601685985 | | 2007 | 0.45517095374189 | | 2006 | 2.0635263612792 | | 2005 | 1.3134851138354 | | 2004 | 0.38163777123543 | | 2003 | 0.70275612166467 | | 2002 | 5.7723577235772 | | 2001 | 1.1513157894737 | | 2000 | 1.0326409495549 | | 1999 | 5.1810237203495 | | 1998 | 5.4919004346108 | | 1997 | 8.9695752009185 | | 1996 | 11.416693316278 | | 1995 | 9.9314466514327 | | 1994 | 12.275508190251 | | 1993 | 10.923817863398 | | 1992 | 12.015693967631 | | 1991 | 19.13526146655 | | 1990 | 17.185895241356 | | 1989 | 20.354346930367 | | 1988 | 16.402877697842 | | 1987 | 19.074814391776 | | 1986 | 47.888513513514 | | 1985 | 309.93169918147 | | 1984 | 373.21565313136 | | 1983 | 145.95153922349 | | 1982 | 120.36435136954 | | 1981 | 116.80003443745 | | 1980 | 131.02499551568 | | 1979 | 78.310035593149 | | 1978 | 50.550924648728 | | 1977 | 34.616714870824 | | 1976 | 31.310865331217 | | 1975 | 39.30673102383 | | 1974 | 39.679970451457 | | 1973 | 20.032377102494 | | 1972 | 12.88147082184 | | 1971 | 11.972568164479 | | 1970 | 6.1107420359874 | | 1969 | 2.458054256178 | | 1968 | 2.0792218581362 | | 1967 | 1.7060931600593 | | 1966 | 7.9303675444846 | | 1965 | 7.7083332642049 | | 1964 | 5.1727504232882 | | 1963 | 6.5811373646406 | | 1962 | 9.4081940682656 | | 1961 | 6.7898234044024 | | 1960 | 2.2281124206708 |
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