Year	Percent
1984	21.1
1992	20.3
1994	19.6
1996	20.2
1998	20.6
2000	19.3
2002	19.8
2004	19.6
2005	19.8
2006	19.8
2008	20.6
2010	20.5
2012	20.3
2014	19.6
2016	20.4