Year	Percent
1998	27.615
1999	26.2402
2000	20.9729
2001	24.2915
2002	25.2065
2003	16.1135
2004	15.599
2005	12.8177
2006	11.9302
2007	10.9751
2008	14.008
2009	36.4246
2010	37.3388
2011	31.3161
2012	27.7928
2013	21.8437
2014	19.3666
2015	18.0245
2016	21.359
2017	18.2645