Year	% of total
1990	21.72269290546295
1991	21.520864645449223
1992	19.302052233419147
1993	19.270048225592017
1994	18.920966354873627
1995	18.67866822666489
1996	19.083220500472034
1997	18.725071438209323
1998	18.774344053414243
1999	19.643516611075324
2000	19.13149948968781
2001	19.30034003955328
2002	18.9970870607077
2003	19.06457486503724
2004	18.313355334211163
2005	17.943546453599037
2006	17.377924134105132
2007	17.010802970696588
2008	16.907546664533474
2009	16.343278748807638
2010	16.607453359207398
2011	16.169008950972817
2012	15.775612085167058
2013	15.67311716901136
2014	15.838487413511693
2015	16.123823935426604
2016	16.355639685204757