Year	Percent
1980	9.5
1988	12.9
1992	17.2
1993	20.3
1994	20.3
1998	22
1999	22
2003	25.2
2006	16.6
2008	23.5
2011	34.7
2013	19.8
2014	26.7
2015	34.7
2016	30.6
2017	33