| Year | Value | | 2023 | 3.7815432 | | 2022 | 3.93361248 | | 2021 | 2.974346814 | | 2020 | 9.9972456 | | 2018 | 0.665035317 | | 2017 | 0.665035317 | | 2016 | 0.804947441 | | 2015 | 0.79610713578782 | | 2014 | 0.7104904556552 | | 2013 | 32.681952 | | 2012 | 47.288226041584 | | 2011 | 44.684921312292 | | 2010 | 25.138924086 | | 2009 | 6.775 | | 2008 | 7.464 | | 2007 | 7.692 | | 2006 | 8.547 | | 2005 | 22.252 | | 2004 | 20.823 | | 2003 | 18.494 | | 2002 | 25.813 | | 2001 | 158.174 | | 2000 | 162.987 | | 1999 | 158.1999969482 | | 1998 | 156.8999938965 | | 1997 | 153.1000061035 | | 1996 | 152.8999938965 | | 1995 | 144.3999938965 | | 1994 | 130.8000030518 | | 1993 | 113.6999969482 | | 1992 | 93.5 | | 1991 | 87 | | 1990 | 64.9000015259 | | 1989 | 64.5999984741 | | 1988 | 73.4000015259 | | 1987 | 66.9000015259 | | 1986 | 12.5 | | 1985 | 11.1000003815 | | 1984 | 11.8999996185 | | 1983 | 10 | | 1982 | 9.3999996185 | | 1981 | 7.5999999046 | | 1980 | 3.2000000477 |
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