Year	Percent
1987	14.7
1988	13.9
1989	16.3
1990	15.8
1991	16.98
1992	15.68
1993	15.69
1995	22.86
1996	17.76
1997	16.67
1998	19.12
1999	13.94
2000	13.58
2001	12.46
2002	11.59
2003	11.92
2004	10.83
2005	11.01
2006	9.67
2007	9.56
2008	9.57
2009	8.96
2010	9.09
2011	8.91
2012	8.99
2013	9.23
2014	9.7
2015	9.46
2016	9.3