Year	% of total
1990	20.28396836676871
1991	20.37695796249503
1992	19.530655017598075
1993	19.914984465826922
1994	19.841764383155535
1995	19.8711678500985
1996	20.21198295524626
1997	19.971680179861814
1998	19.977343972383036
1999	20.796634619686092
2000	20.76691561269942
2001	20.537776308007068
2002	20.793049700468334
2003	20.748549360141606
2004	20.34350567442355
2005	20.167775141813397
2006	19.92132712139946
2007	19.93093894475001
2008	20.247965201157793
2009	20.111927928435872
2010	20.401136790075338
2011	20.213904906621153
2012	20.249265382475134
2013	20.18181491188973
2014	20.320253942285692
2015	20.65949623112269
2016	21.176027147136807