Year	Percent
1974	1.47
1976	2.1
1978	1.87
1979	1.62
1980	2.94
1981	3.22
1982	3.43
1983	2.86
1984	3.94
1985	4.86
1990	8.751
1991	8.886
1992	9.535
1993	8.78
1994	6.132
1995	5.572
1996	6.176
1997	7.442
1998	8.459
1999	9.509
2000	9.141
2001	9.889
2002	11.435
2003	11.553
2004	10.785
2005	9.712
2006	8.733
2007	7.409
2008	6.702
2009	9.002
2010	7.966
2011	6.505
2012	6.052
2013	5.518
2014	5.303
2015	4.491
2016	4.008
2017	3.661