Year	Percent
1983	13.7373
1985	12.3837
1987	13.9714
1988	12.6479
1989	11.8088
1990	10.8898
1991	9.9073
1992	7.7943
1993	7.6873
1994	8.0531
1995	8.6623
1996	8.1126
1997	7.1438
1998	5.8095
1999	4.8523
2000	3.4602
2001	2.515
2002	2.8866
2003	3.795
2004	5.0404
2005	5.0668
2006	4.3599
2007	3.6349
2008	3.0072
2009	3.4641
2010	4.5111
2011	5.4141
2012	6.2288
2013	7.3021
2014	7.7455
2015	7.2731
2016	6.5068
2017	5.2549