Year	Percent
1986	24.86
1987	20.91
1992	19.49
1996	22.62
2001	34.762
2002	35.449
2003	33.743
2004	33.604
2005	31.217
2007	28.568
2008	29.607
2009	30.851
2010	28.6075
2011	26.6937
2012	25.4558
2013	24.2413
2014	22.737
2015	22.5135
2016	22.8058
2017	23.2421