Year	Percent
2004	37.8168
2005	38.4263
2006	37.2017
2007	35.5431
2008	34.1574
2009	32.8164
2010	32.2399
2011	30.7892
2012	30.3324
2013	29.0204
2014	28.6193
2015	25.0628
2016	22.7252
2017	21.8212