Year	Percent
1970	6.5
1971	7.1
1972	7.7
1973	7.8
1974	7
1981	5.1
1982	9.1
1984	9.27
1986	8.5
1987	6.7
1990	6.85
1991	7.15
1992	6.83
1993	6.47
1994	6.95
1995	7.86
1998	7.47
1999	8.7
2000	10.6
2001	11.19
2002	13.5
2003	13.04
2004	10.1019
2005	9.3557
2006	8.1527
2007	6.7122
2008	5.6208
2009	5.5066
2010	5.2711
2011	4.8402
2012	4.9055
2013	4.9946
2014	5.0551
2015	6.3584
2016	6.4955
2017	6.5568