Year | Value | 2020 | 0.104 | 2018 | 0.076 | 2009 | 0.025 | 2008 | 0.025 | 2007 | 0.022 | 2006 | 0.027 | 2005 | 0.032 | 2004 | 0.027 | 2003 | 0.027 | 2002 | 0.029 | 2001 | 0.028 | 2000 | 0.021 | 1999 | 0.02 | 1998 | 0.021 | 1997 | 0.023 | 1996 | 0.025 | 1994 | 0.029 | 1988 | 0.031 | 1984 | 0.013 | 1981 | 0.011 | 1980 | 0.011 | 1975 | 0.012 | 1970 | 0.012 | 1965 | 0.014 | 1960 | 0.009 |
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