Year | Value | 2021 | 2.77 | 2020 | 2.718 | 2019 | 3.208 | 2018 | 2.87 | 2017 | 2.999 | 2016 | 2.881 | 2015 | 2.705 | 2014 | 2.617 | 2013 | 2.516 | 2012 | 2.433 | 2011 | 2.348 | 2010 | 2.283 | 2009 | 2.197 | 2008 | 2.139 | 2007 | 2.074 | 2006 | 2.026 | 2000 | 1.308 | 1999 | 1.719 | 1998 | 0.901 | 1997 | 0.872 | 1996 | 0.864 | 1995 | 0.854 | 1994 | 0.845 | 1993 | 0.883 | 1990 | 1.26 | 1988 | 0.881 | 1987 | 0.968 | 1984 | 0.99 | 1979 | 0.679 | 1970 | 0.614 | 1965 | 0.517 | 1960 | 0.391 |
|