Year	% of total
1990	31.476342320811042
1991	30.67557930715936
1992	32.847688308330696
1993	31.844288939382828
1994	32.47146296659861
1995	32.380331095042884
1996	34.79999300762329
1997	33.166603654333336
1998	34.76632874608401
1999	34.52147992017452
2000	35.29107912155311
2001	34.32990885338665
2002	31.952973197469362
2003	30.965607615175532
2004	29.38964774073353
2005	28.490900087768285
2006	28.331406846481325
2007	27.199400458607354
2008	30.045886183796412
2009	30.51626531199492
2010	27.029358601901034
2011	25.644117176947148
2012	25.078907525462657
2013	25.698145180461665
2014	26.040155693876066
2015	29.4728915447426
2016	31.238582917815513