Year	% of total
1990	31.476342320811046
1991	30.67557930715936
1992	32.84768830833069
1993	31.84428893938282
1994	32.47146296659861
1995	32.380331095042884
1996	34.799993007623286
1997	33.16660365433333
1998	34.766328746084
1999	34.521479920174514
2000	35.2910791215531
2001	34.32990885338664
2002	31.952973197469362
2003	30.965607615175525
2004	29.389647740733526
2005	28.490900087768285
2006	28.331406846481325
2007	27.199400458607347
2008	30.045886183796416
2009	30.51626531199492
2010	27.029358601901034
2011	25.644117176947148
2012	25.078907525462665
2013	25.698145180461662
2014	26.040155693876063
2015	29.4728915447426
2016	31.238582917815506