Year	% of total
1990	21.34437774805738
1991	22.098220537172246
1992	23.048321767758356
1993	23.187565952357062
1994	22.29491950844609
1995	21.97670718859875
1996	23.7211061153538
1997	25.074371501512413
1998	23.30317338691663
1999	24.048303993798488
2000	25.35470190920579
2001	24.313367657199358
2002	22.728221609090564
2003	21.581884499742348
2004	21.244322420811528
2005	19.099867617501555
2006	17.646615319133897
2007	16.680152769184943
2008	16.863727409320102
2009	15.95353293310362
2010	16.455408160273834
2011	15.507379051512457
2012	15.716504815417291
2013	15.883184511777579
2014	16.10292668220802
2015	16.715276334780047
2016	16.886577598234663