Year	% of total
1990	18.840913627445538
1991	19.52443871044409
1992	20.94496150054501
1993	22.008126634756525
1994	22.447622679200318
1995	22.0106047415666
1996	22.29738905823164
1997	22.201181436244042
1998	22.324297713582283
1999	23.349151693811727
2000	21.918301617360992
2001	22.018275767448777
2002	23.073160326895838
2003	23.658532747889968
2004	24.204949497497395
2005	24.65811028074951
2006	24.74786006736046
2007	23.898311287259883
2008	23.926466868124102
2009	23.74797323559406
2010	24.267770857208546
2011	24.320191947049945
2012	23.418585986201762
2013	23.337589095468104
2014	22.94270061641381
2015	24.68573937469827
2016	24.867877365946267