Year	Percent
1978	6.21
1979	6.39
1980	4.57
1982	4.64
1983	5.09
1984	4.76
1985	7.79
1986	9.82
1987	7.98
1988	5.64
1989	4.36
1991	4.19
1992	7.91
1993	8.69
1994	9.07
1995	8.09
1996	10.68
1997	6.62
1998	11.17
1999	13.12
2001	10.67
2002	16.35
2003	15.07
2004	15.26
2006	11.57
2007	11.18
2008	12.18
2009	16.61
2010	12.53
2011	12.05
2012	11.76
2013	13.3
2014	11.83
2015	11.17
2016	12.5