Year	Percent
1980	9.119
1981	7.166
1982	7.451
1983	6.535
1984	6.596
1985	7.353
1986	6.488
1987	6.039
1988	5.534
1989	5.364
1990	5.464
1991	5.797
1992	6.561
1993	7.069
1994	5.989
1995	5.291
1996	4.774
1997	6.538
1998	12.732
1999	11.683
2000	9.0116
2001	8.7081
2002	7.3916
2003	8.9821
2004	9.3529
2005	8.9893
2006	8.9613
2007	7.194
2008	7.9477
2009	8.5677
2010	8.9775
2011	8.1098
2012	8.5133
2013	9.034
2014	9.2033
2015	9.9676
2016	10.4687
2017	9.7158