Year	Percent
1997	13.308
1998	11.62156
2000	13.78428
2002	15.28406
2003	14.54183
2004	12.15936
2005	11.45196
2006	10.44302
2007	11.19116
2008	13.8841
2009	16.07463
2010	14.51348
2011	14.94713
2012	16.76682
2013	15.69016
2014	14.04271
2015	15.09954