Year	Percent
1973	8.6
1975	21.2
1977	20.86
1979	14.7
1986	12.09
1988	11.02
1989	11.59
1990	7.77
1991	12.17
1992	14.81
1993	12.72
1994	13.83
1995	10.83
1996	11.46
1997	9.76
1998	7.65
1999	7.45
2001	6.87
2002	9.05
2003	10.84
2004	10.2
2005	10.2
2006	7.54
2007	7.88
2008	8.18
2009	14.25
2011	14.52
2012	14.02
2013	16.18
2014	13.8
2015	12
2016	12.7
2017	9.8
2018	10