| Year | Value | | 2022 | 0.5698475549865 | | 2021 | 0.99503076984069 | | 2020 | 1.4025774113155 | | 2019 | 1.2996127850461 | | 2018 | 1.290815628796 | | 2017 | 1.2533426891233 | | 2016 | 1.1541282758457 | | 2015 | 1.0848654709789 | | 2014 | 0.95165217003539 | | 2013 | 0.84369330009509 | | 2012 | 0.82554322037368 | | 2011 | 0.87817534560162 | | 2010 | 0.90521039561471 | | 2009 | 0.98101564811187 | | 2008 | 1.0088810754039 | | 2007 | 0.91439966847809 | | 2006 | 0.80581513479929 | | 2005 | 1.4104858368743 | | 2004 | 2.8093248337513 | | 2003 | 2.1997168274369 | | 2002 | 2.2932866809793 | | 2001 | 2.0179456234118 | | 2000 | 1.765977248429 | | 1996 | 0.78783093358105 | | 1995 | 0.91552038608376 | | 1994 | 1.0059367209463 | | 1993 | 0.95095223597862 | | 1992 | 0.9696923011084 | | 1991 | 0.58289277831956 | | 1990 | 0.90582827960421 | | 1989 | 1.5837366892546 | | 1988 | 2.6637660140198 | | 1987 | 3.0860887697349 | | 1986 | 5.3558558558559 | | 1985 | 8.4368635437882 | | 1984 | 4.6747058823529 | | 1983 | 4.516348773842 | | 1982 | 5.1265560165975 | | 1981 | 3.9448966812774 | | 1980 | 3.7002652519894 | | 1979 | 3.7150127226463 | | 1978 | 3.8908450704225 | | 1977 | 6.0745829244357 | | 1976 | 8.3526011560694 | | 1975 | 6.9581056466302 | | 1974 | 2.8505747126437 | | 1973 | 1.6459627329193 |
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