Year Million km2
1979 1.1
1980 3.3
1981 3.1
1982 10.8
1983 12.2
1984 14.7
1985 18.8
1986 14.4
1987 22.4
1988 13.8
1989 21.7
1990 21.1
1991 22.6
1992 24.9
1993 25.8
1994 25.2
1996 26.9
1997 25.1
1998 27.9
1999 25.8
2000 29.9
2001 26.5
2002 21.9
2003 28.4
2004 22.8
2005 27.3
2006 29.6
2007 25.2
2008 27
2009 24.4
2010 22.6
2011 26.1
2012 21.1
2013 24
2014 24.1
2015 28.2
2016 23.0