Year	Percent
1978	0.72
1979	0.43
1986	2.37
1987	2.56
1988	2.34
1989	1.82
1990	1.74
1991	1.91
1992	2.03
1993	3.36
1994	3.67
1995	4.01
1996	4.97
1997	5.15
1998	3.43
1999	3.58
2000	3.25
2001	2.49
2002	3.44
2003	4.29
2004	5.63
2005	6.1
2006	6.31
2007	6.52
2008	6.59
2009	7.64
2010	8.89
2011	10.84
2012	12.74
2013	13.7
2014	13.48
2015	12.45
2016	10.97
2017	8.54
2018	6.53
2019	6.21
2020	5.86