Year	% (national estimate)
1970	53.35
1980	58.72
1983	57.66
1986	55.74
1987	54.96
1988	57.94
1989	58.6
1990	62.18
1991	60.58
1992	58.59
1994	56.22
1995	61.4
1996	60.65
1997	58.08
2003	54.02
2004	51.67
2011	49.45
2012	42.47
2013	41.82
2014	46.1
2015	37.981
2016	42.956
2017	39.471
2018	40.392
2019	41.947