Year | Value | 2019 | 2.513 | 2017 | 2.226 | 2015 | 2.741 | 2014 | 2.27 | 2013 | 2.43 | 2010 | 2.339 | 2009 | 2.164 | 2008 | 2.198 | 2007 | 2.36 | 2006 | 2.259 | 2005 | 2.273 | 2004 | 2.06 | 2003 | 2.293 | 2002 | 2.221 | 2001 | 2.058 | 2000 | 1.894 | 1999 | 1.957 | 1998 | 1.009 | 1997 | 1.66 | 1994 | 1.625 | 1991 | 1.348 | 1984 | 1.159 | 1982 | 1.128 | 1981 | 1.114 | 1980 | 0.786 | 1975 | 0.378 | 1970 | 0.404 | 1965 | 0.37 | 1960 | 0.346 |
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