Year	% of total
1990	3.194802779480626
1991	3.60922938159297
1992	3.652006508498276
1993	3.9433459815192675
1994	3.819544903563294
1995	3.718634920396487
1996	3.8424969918234173
1997	3.932085205772691
1998	3.920232877491769
1999	4.47971283052239
2000	4.957196375044727
2001	4.49815249896342
2002	4.418927404790502
2003	5.539616847874871
2004	6.1250732702170225
2005	6.081178929168973
2006	6.06581468877404
2007	6.057376127962691
2008	5.870469381938975
2009	5.684846722803559
2010	6.047029604874926
2011	7.1438252650933345
2012	7.038008454783858
2013	6.82995453986805
2014	7.278424692935393
2015	7.759079933149047
2016	7.7189485986928945