Year	Percent
1990	10.976
1991	12.025
1992	12.583
1993	13.194
1994	12.057
1995	18.2864
1996	15.6559
1997	14.6747
1998	12.9911
1999	11.4545
2000	11.3529
2001	12.0476
2002	12.2912
2003	11.3421
2004	11.6704
2005	10.7278
2006	8.6282
2007	6.5802
2008	6.5974
2009	7.8671
2010	7.5089
2011	7.6876
2012	6.9472
2013	7.5304
2014	6.6093
2015	8.5931
2016	9.2659
2017	8.9973