Year	Percent
1974	5.21
1975	4.86
1976	5.23
1977	7.14
1978	6.19
1979	6.71
1982	6.27
1983	7.68
1984	8.25
1985	9.49
1986	8.7
1987	9.42
1988	14
1989	13.68
1991	12.82
1992	10.8
1993	9.71
1994	10.67
1995	10.75
1996	11.3
1997	10.73
1998	10.27
1999	8.87
2000	11.06
2001	12.24
2002	11.18
2003	10.55
2004	9.47
2005	8.11
2006	7.19
2007	5.27
2009	5.11
2010	2.8781
2011	2.0798
2012	1.9737
2013	1.8058
2014	2.2036
2015	2.3859
2016	2.8989
2017	3.0835