Year	Percent
1976	1.92
1977	1.29
1978	2.48
1980	1.66
1982	2.85
1985	2.1
1986	2.59
1987	2.55
1988	2.74
1990	2.54
1991	2.62
1992	2.73
1993	2.78
1994	4.37
1996	4.86
1997	4.68
1998	5.46
1999	6.36
2000	6.08
2001	6.08
2002	6.6
2003	6.66
2004	7.3
2005	7.94
2006	7.55
2007	8.06
2008	7.21
2009	6.11
2010	5.61
2011	5.15
2012	4.47
2013	4.34
2014	4.05
2015	4.51
2016	4.3
2017	3.78
2018	4.39
2019	3.6
2020	4.28