Year % of total 1990 0.01607200257152041 1991 0.015693659761456372 1992 0.016202203499675955 1993 0.016742005692281934 1994 0.015509887553315237 1995 0.1161620072794858 1996 0.06126981695642184 1997 0.07589556769884638 1998 0.793997668997669 1999 1.2969386216256975 2000 2.1506165590135056 2001 2.04617724319093 2002 1.972872996300863 2003 2.677279305354559 2004 2.3443127496562113 2005 2.242508434213138 2006 2.4545153820707903 2007 3.0113674134148773 2008 2.902616013171535 2009 3.6151923428641104 2010 3.3712703783451246 2011 3.0725730442978323 2012 3.4152302546951376 2013 3.219684989562907 2014 2.179106216861854 2015 2.726597826820544