Year	Percent
1978	3.15
1979	3.25
1980	3.21
1982	4.18
1983	4.39
1984	4.95
1985	5.02
1986	6.21
1987	6.45
1988	6.88
1989	7.36
1990	6.6
1991	6.99
1992	6.43
1993	7.22
1994	8.34
1995	8.82
1996	9.01
1997	9.38
1998	9.79
1999	9.51
2000	8.79
2001	7.96
2002	7.78
2003	7.46
2004	6.54
2005	6.65
2006	5.88
2007	5.31
2008	5.96
2009	6.93
2010	7.51
2011	7.47
2012	9.59
2013	11.2
2014	11.85
2015	11.16
2016	11.11
2017	10.85
2018	10.35
2019	9.81
2020	8.99