Year	Percent
1992	14.701
1993	15.6
1994	15.994
1995	14.742
1996	13.938
1997	12.9905
1998	11.8107
1999	13.1687
2000	18.3231
2001	20.017
2002	20.6771
2003	19.9268
2004	19.7664
2005	19.1373
2006	14.9193
2007	10.3372
2008	7.9501
2009	8.6597
2010	10.0226
2011	10.3991
2012	10.9074
2013	11.1115
2014	9.5918
2015	7.7092
2016	6.226
2017	4.9076