Year	% of total
1990	21.83733988745693
1991	21.708442716839826
1992	19.557001047100307
1993	19.329816954609555
1994	18.898618321366385
1995	18.556620818576327
1996	18.97994269526051
1997	18.585111621241317
1998	18.363133767197713
1999	19.265313548927836
2000	18.90911310079133
2001	19.009338270271556
2002	18.711884522171687
2003	18.746167111566596
2004	17.980185847293768
2005	17.668026168563554
2006	17.0459213176253
2007	16.740103253784497
2008	16.708454697578762
2009	16.103954757208786
2010	16.304208735661117
2011	15.950546438545652
2012	15.546816781947468
2013	15.46243153118175
2014	15.645814528610567
2015	15.935699015602648
2016	16.178191494727795