Year	Percent
1987	6.35
1988	4.93
1989	4.87
1990	4.67
1991	4.14
1992	3.51
1993	3.28
1994	3.3
1995	3.22
1996	2.9
1997	2.64
1998	2.98
1999	2.37
2000	2.2
2001	2.55
2003	2.12
2004	1.78
2005	1.66
2006	1.69
2007	1.28
2008	0.92
2009	1.18
2010	2.79
2011	1.15
2012	0.9
2013	1.29
2014	1.46
2015	1.65
2016	1.4
2017	1.29