Year	Percent
1974	1.62
1990	4.537
1991	8.078
1992	9.707
1993	9.43
1994	6.638
1995	6.188
1996	6.732
1997	7.128
1998	10.137
1999	10.118
2000	10.529
2001	9.867
2002	9.369
2003	9.237
2004	9.855
2005	10.027
2006	8.748
2007	7.459
2008	5.903
2009	7.157
2010	6.854
2011	5.892
2012	5.118
2013	5.03
2014	4.287
2015	4.369
2016	4.456
2017	3.79