Year	% of total
1990	20.838340888171015
1991	22.022941164532657
1992	20.449324129751606
1993	21.763834390103522
1994	23.18850226931877
1995	26.053334153519796
1996	26.39102121350826
1997	24.558294777837343
1998	28.613568340663896
1999	29.69212045622534
2000	29.3338375667503
2001	29.350496871071073
2002	32.04682445827947
2003	33.25251053263317
2004	33.407162116488884
2005	37.03383974045746
2006	36.63705144731352
2007	37.274661476333875
2008	37.393645189988746
2009	37.54648139157561
2010	38.68039748802952
2011	40.08365003239709
2012	38.701616778828814
2013	38.23669786945898
2014	39.81506926483288
2015	42.59481581998646
2016	44.74111998156813