Year	% of total
1990	23.706203792992607
1991	28.311362209667294
1992	27.730071289695395
1993	25.405993638037838
1994	26.359053896859248
1995	25.18392317819252
1996	28.130504710117176
1997	23.466909532483303
1998	25.123834498834498
1999	28.208415020358917
2000	28.141514973576044
2001	26.24084059173234
2002	22.688039457459926
2003	21.396526772793052
2004	26.808984349420474
2005	22.894754250181915
2006	23.757856434005955
2007	21.711094861397328
2008	24.50149399353619
2009	28.74474181552155
2010	27.79452476161181
2011	22.381401193842287
2012	25.077180344738874
2013	29.28078942374597
2014	35.49496008856261
2015	25.700209219140174