Year	Percent
1988	2.49
1989	2.25
1990	3.87
1991	3.48
1992	4.04
1993	3.81
1994	3.41
1995	3.5
1996	3.87
1997	2.42
1998	4.05
1999	3.01
2000	7.37
2001	6.86
2002	3.02
2003	4.9
2004	6.3
2005	5.53
2006	6.68
2007	5.69
2008	5.75
2009	5.83
2010	5.18
2011	4.62
2012	5.19
2013	4.92
2014	4.17
2015	5.15
2016	6.49
2017	6.87