Year	% of total
1990	23.595420226845462
1991	24.372153402354645
1992	22.558338013391207
1993	19.165791121793717
1994	20.97676253172649
1995	24.069899708246208
1996	23.290012871757796
1997	24.72871638374801
1998	24.053729998608876
1999	21.595429082787803
2000	21.866437453104766
2001	18.266450956694857
2002	17.045651642475754
2003	20.740718268413872
2004	22.95533198183888
2005	17.366797329162175
2006	23.665647119708986
2007	24.595878523715864
2008	24.40995028352659
2009	28.889110080249125
2010	22.357491529851668
2011	26.196024587262936
2012	23.760705230279473
2013	24.19179948764214
2014	27.18698126751749
2015	27.860216676390714
2016	28.15431931901651