Year	% of total
1991	17.151145008285617
1992	17.463522427436104
1993	18.220688399188447
1994	18.1284987572574
1995	19.347468383517437
1996	20.619703224644805
1997	20.563788726821027
1998	21.05393126613699
1999	21.89090912197158
2000	22.39667187130959
2001	22.799473961843848
2002	22.980390544191764
2003	23.59946150173754
2004	24.25098690767221
2005	25.28932181883718
2006	25.38454174581072
2007	25.43159014585592
2008	26.61500321171937
2009	27.18737966272392
2010	28.41925631167749
2011	26.945040050590816
2012	26.792153077618426
2013	26.941157864965348
2014	24.852552278620198
2015	22.888780014221584
2016	24.17815968386084