Year	% (national estimate)
1970	23.611469904417465
1981	45.91608391608391
1986	56.09587143252979
1988	56.676762114537446
2004	56.79640718562874
2006	59.03288782099414
2007	60.94497607655502
2008	60.902366863905335
2009	61.38900971436857
2010	61.24450951683749
2011	59.687141216991954
2012	64.14039794321485
2013	65.78645235361653