Year	Percent
1977	4.48
1979	4.67
1983	9.84
1985	9.2
1987	8.22
1988	8.4
1989	7.94
1990	7.16
1991	6.55
1992	5.16
1993	5.56
1994	6.58
1995	6.4
1996	5.62
1997	4.82
1998	3.7
1999	2.95
2000	2.28
2001	1.7
2002	2.18
2003	3.11
2004	4.05
2005	4.79
2006	4.01
2007	3.03
2008	2.48
2009	3.19
2010	3.81
2011	3.94
2012	4.63
2013	6.04
2014	6.18
2015	5.6
2016	4.62
2017	3.7
2018	2.82
2019	2.57
2020	2.89