Year	% of total
1990	21.908236282482417
1991	21.675795380060936
1992	18.736229995446948
1993	18.61468923811462
1994	18.240294113083845
1995	17.99885984395274
1996	18.383858220728563
1997	17.967299842266485
1998	17.887742824551232
1999	18.769408744813425
2000	18.25183619238281
2001	18.48106740507197
2002	18.048479664817105
2003	18.04383649949562
2004	17.294788907436605
2005	17.017970140176203
2006	16.463086570756563
2007	16.143224949310515
2008	16.04977528163504
2009	15.548008144115586
2010	15.80580645616666
2011	15.31374257239336
2012	14.93985436512859
2013	14.938412100166834
2014	15.093452064583541
2015	15.351126098741807
2016	15.694598220137987