Year	Percent
1978	0.79
1979	0.46
1980	0.54
1981	0.6
1982	1.12
1983	1.58
1984	1.42
1985	1.76
1986	1.67
1987	1.15
1988	1
1989	0.95
1990	1.08
1991	0.98
1992	1
1993	0.93
1994	1.1
1995	1.32
1996	2.05
1997	2.2
1998	2.11
1999	2.38
2000	2.45
2001	3.96
2002	4.48
2003	4.32
2004	3.81
2005	3.53
2006	3.39
2007	3.45
2008	3.65
2009	5.41
2010	4.86
2011	3.97
2012	3.79
2013	3.71
2014	3.55
2015	3.43
2016	3.54
2017	3.38
2018	3.32
2019	3.28
2020	3.45