Year	Percent
1977	2.42
1978	2.72
1979	3.47
1980	3.94
1981	3.82
1982	3.85
1983	5.65
1984	4.68
1989	5.5
1990	5.1
1991	5.78
1992	6.35
1993	7.5
1994	7.3
1995	7.38
1997	5.19
1998	4.93
1999	4.94
2000	5.06
2001	5.67
2002	6.22
2003	7.49
2004	5.94
2005	7.1
2006	6.68
2007	5.82
2008	5.531
2009	5.0397
2010	4.7697
2011	8.7696
2012	9.2347
2013	9.7961
2014	9.7295
2015	9.3923
2016	8.8361
2017	8.25