Year	Percent
1988	4.06
1989	4.39
1990	6.53
1991	6.05
1992	6.97
1993	6.41
1994	6.33
1995	6.97
1996	6.54
1997	4.81
1998	6.66
1999	5.68
2000	11.41
2001	12.57
2002	5.17
2003	8.73
2004	11.52
2005	9.77
2006	11.7
2007	10.42
2008	10.46
2009	10.59
2010	9.33
2011	9.08
2012	9.78
2013	9.43
2014	8.18
2015	9.98
2016	11.87
2017	12.59