Year	% (national estimate)
1960	38.27874116891458
1970	50.23031120098865
1980	54.050952490245585
2000	67.40522540983606
2001	68.0947450168263
2002	68.09993425378042
2003	69.74678509876706
2004	71.16763631443648
2005	71.69042769857434
2006	71.38794854434666
2007	72.56565656565657
2008	73.25468424705066
2009	73.76244565979526
2010	74.21401381643874
2011	76.05398636426881
2012	76.01854453498173
2013	75.83959189457278
2014	76.3499073942157
2015	77.2530953066513
2016	77.47093023255815
2017	77.97356828193833