Year	% of total
1990	39.617379938028435
1991	39.58835841216046
1992	33.48100808708551
1993	33.025927204243914
1994	31.74731446758951
1995	31.252768091115193
1996	31.502874014368977
1997	32.19843144655712
1998	32.645921147066595
1999	33.36688003837375
2000	33.202061053775694
2001	32.71312226753135
2002	31.179465732113773
2003	30.166363447277917
2004	29.28251838076946
2005	27.28748879910652
2006	26.21731501261644
2007	24.832518117033885
2008	25.537225990686494
2009	25.199876754467386
2010	24.263886904364735
2011	23.43758726666946
2012	23.676166699310233
2013	23.614361069188476
2014	24.00216757944843
2015	24.52148151303229
2016	24.928837867871284