Year	Percent
1987	8.83
1988	8.59
1989	8.92
1990	6.55
1991	6.27
1992	6.18
1993	6.93
1994	6.76
1995	5.97
1996	4.27
1997	4.23
1998	4.03
1999	3.46
2000	2.9
2001	2.18
2002	1.94
2003	1.97
2004	1.77
2005	1.74
2009	1.34
2010	1.38
2011	1.44
2012	0.99
2013	0.98
2014	0.67
2015	0.56
2016	0.79