Year	% of total
1990	20.838340888171015
1991	22.022941164532654
1992	20.449324129751602
1993	21.763834390103522
1994	23.188502269318768
1995	26.053334153519796
1996	26.39102121350826
1997	24.558294777837343
1998	28.613568340663896
1999	29.69212045622534
2000	29.333837566750308
2001	29.350496871071073
2002	32.04682445827947
2003	33.25251053263317
2004	33.407162116488884
2005	37.03383974045745
2006	36.63705144731351
2007	37.27466147633387
2008	37.393645189988746
2009	37.54648139157562
2010	38.68039748802953
2011	40.083650032397095
2012	38.70161677882883
2013	38.23669786945897
2014	39.815069264832886
2015	42.59481581998645
2016	44.74111998156815