Year	Percent
1990	1.504
1991	3.652
1992	7.626
1993	12.03
1994	12.513
1995	13.2778
1996	12.1191
1997	12.1842
1998	10.1956
1999	9.2227
2000	8.8275
2001	7.6
2002	7.1981
2003	6.6069
2004	7.7357
2005	7.1845
2006	6.6113
2007	5.7864
2008	5.4276
2009	6.1195
2010	6.2112
2011	5.5971
2012	5.6152
2013	6.2592
2014	6.5571
2015	7.5205
2016	7.3528
2017	6.8824