Year	Percent
1978	5.3
1979	5.4
1980	4.9
1981	3.8
1982	3.2
1983	2.3
1984	1.9
1985	1.8
1986	2
1987	2
1988	2
1989	2.6
1990	2.5
1991	2.3
1992	2.3
1993	2.6
1994	2.8
1995	2.9
1996	3
1997	3.1
1998	3.1
1999	3.1
2000	3.1
2001	3.6
2002	4
2003	4.3
2004	4.2
2005	4.2
2006	4.1
2007	4
2008	4.2
2009	4.3
2010	4.1
2011	4.1
2012	4.1
2013	4.05
2014	4.1
2017	3.9
2018	3.8
2019	5.15