Year	Percent
1975	7.01
1976	6.34
1977	5.11
1978	4.98
1979	5.81
1980	5.89
1981	7
1982	8.05
1983	11.49
1984	12.86
1985	13.16
1986	10.93
1987	9.1
1988	7.28
1989	9.74
1990	13.96
1994	8.56
1995	10.24
1996	11.77
2001	8.83
2002	16.17
2003	16.78
2005	10.66
2006	8.61
2007	7.28
2008	6.25
2009	6.1
2010	7.11
2011	6.9
2012	6.6
2016	5.32
2017	5.05