Year	% of total
1990	39.791653645782326
1991	39.997878567953286
1992	32.33218895076136
1993	31.933111911750064
1994	30.256223011838284
1995	29.52553975105899
1996	29.91196526173794
1997	30.687333551561345
1998	30.455413111744477
1999	31.060850686926063
2000	30.489391887326146
2001	29.975823129062775
2002	28.2710867618266
2003	27.188756495966093
2004	26.683667910493472
2005	24.554522658991587
2006	23.522571618089525
2007	22.050941959638898
2008	22.472476769394163
2009	21.62568828285321
2010	21.169926074257212
2011	20.60091785138355
2012	20.847994620534788
2013	20.810844771982758
2014	21.17894780207551
2015	21.506405068260836
2016	21.883737994201912