Year	Percent
1997	26.64939
1998	17.78061
1999	24.09367
2000	18.84232
2001	18.81664
2002	20.8871
2003	24.05037
2004	27.06916
2005	31.73748
2006	45.14905
2007	67.91211
2008	31.4198
2009	59.31201
2010	70.05235
2011	47.66963
2012	53.26615
2013	40.24374
2014	39.20808
2015	29.77767
2016	42.31325
2017	46.93614