Year	% of total
1990	15.944043575925964
1991	16.278823012960924
1992	16.217666549284285
1993	14.74767277597273
1994	14.45873879125467
1995	15.467746844341344
1996	15.82285563764137
1997	16.12252299097124
1998	16.05563276253519
1999	16.798354957655736
2000	18.208752254593946
2001	18.188177436762558
2002	19.5941605540172
2003	20.80102709596921
2004	22.31920317950172
2005	21.99666156360587
2006	22.999430945769074
2007	22.24332678202631
2008	22.90674384486273
2009	23.50959622810142
2010	23.667500294589853
2011	23.4793729533963
2012	24.369635755953706
2013	24.613474700191404
2014	25.306838066693206
2015	25.916669265997765
2016	26.09467480812712