Year	% (national estimate)
1974	72
1975	71.2
1976	68.23
1978	66.8
1980	63.99
1981	65.4
1982	65.99
1985	65.72
1988	67.12
1990	69.6
1994	67.11
1995	68.51
1996	67.95
1997	67.7
1998	66.38
1999	65.87
2001	65.73
2007	69.5
2008	70.604
2009	67.708
2010	65.742
2011	65.512
2012	64.601
2013	64.13
2014	64.783
2015	63.3
2016	66.063
2017	66.982
2018	67.283
2019	68.697
2020	65.322
2021	66.97
2022	68.831