Year	Percent
1974	1.77
1975	4.5
1976	6.4
1978	7.89
1979	7.94
1983	7.3
1985	8.18
1986	8.7
1987	7.38
1988	6.01
1989	5.13
1990	4.64
1991	3.92
1992	3.98
1993	5.3
1994	6.71
1995	7.06
1996	7.3
1997	6.57
1998	4.65
1999	4.58
2000	3.81
2001	3.83
2002	4.5
2003	6.13
2004	6.32
2005	7.58
2006	7.65
2007	7.96
2008	7.55
2009	9.43
2010	10.77
2011	12.68
2012	15.53
2013	16.18
2014	13.89
2015	12.44
2016	11.07
2017	8.87
2018	6.99
2019	6.46
2020	6.79