Year	Percent
1983	6.2442
1984	6.1148
1985	5.9697
1986	5.9062
1987	6.3265
1988	6.1874
1989	4.6246
1990	3.9927
1991	3.9485
1992	4.2504
1993	5.0865
1994	6.4413
1995	6.2327
1996	6.5669
1997	6.1743
1998	6.6198
1999	6.1433
2000	4.6214
2001	4.832
2002	5.4319
2003	6.5892
2004	5.9741
2005	6.5714
2006	6.5222
2007	5.9498
2008	5.6797
2009	6.6843
2010	7.1851
2011	6.4158
2012	6.8654
2013	7.5456
2014	8.1965
2015	8.1626
2016	7.3173
2017	6.279