Year	% of total
1990	21.331126981241873
1991	21.236417062218603
1992	19.234999997920646
1993	19.033613335188797
1994	18.61866578770062
1995	18.31119344976072
1996	18.74350196868673
1997	18.401410380521373
1998	18.21774253758094
1999	19.09661660292807
2000	18.73908015331358
2001	18.817876153493675
2002	18.556900478551608
2003	18.59009006767049
2004	17.839139078374632
2005	17.50364533970077
2006	16.89282117613892
2007	16.60383679629883
2008	16.56014005576236
2009	16.00285865367263
2010	16.237733795067992
2011	15.886601974646004
2012	15.477962482802528
2013	15.403057448904724
2014	15.581269630986647
2015	15.875541488031137
2016	16.099831939885263