Year	Percent
1979	3.21
1980	2.87
1981	3.16
1982	3.55
1983	5.92
1984	5.59
1985	6.16
1986	5.45
1987	5.84
1988	5.89
1989	5.29
1990	5.46
1991	7.95
1992	9.51
1993	11.01
1994	9.68
1995	7.63
1996	7.58
1997	6.77
1998	6.29
1999	5.49
2000	4.53
2001	4.58
2002	4.3
2003	3.77
2004	3.55
2005	3.37
2006	3.23
2007	2.73
2008	2.61
2009	3.34
2010	3.25
2011	3.33
2012	3.45
2013	3.83
2014	4.09
2015	4.25
2016	4.25
2017	4.07
2018	4.29
2019	3.98
2020	5.12