Year	% of total
1990	40.39249698092118
1991	40.36470528969425
1992	34.24596519995927
1993	33.83031912059547
1994	32.55797268558595
1995	32.09626928343239
1996	32.42769732255445
1997	33.13287260802783
1998	33.50272190036068
1999	34.20906714011658
2000	34.065589598731265
2001	33.60932851347627
2002	31.961241172176962
2003	31.003025455436514
2004	30.056523878241443
2005	28.094988622684436
2006	27.026659945693375
2007	25.742072083880988
2008	26.435784875424165
2009	26.05822505381304
2010	25.263787402618124
2011	24.438295429650385
2012	24.59145870631844
2013	24.59128152062534
2014	25.013812748911644
2015	25.462891114545812
2016	25.916837003253548