Year	Percent
1984	17.76
1990	20.75
1991	21.21
1992	20.45
1993	19.71
1994	20.02
1995	21.33
1998	20.41
2000	26.59
2001	28.65
2003	34.07
2004	27.9847
2005	25.0615
2006	23.3732
2007	20.7272
2008	17.9286
2009	17.0266
2010	16.7128
2011	15.1785
2012	14.7319
2013	15.8948
2014	16.1179
2015	19.8834
2016	20.1935
2017	20.7343