Year	% (national estimate)
1960	9.404463539801885
1970	10.925433599189773
1981	9.031115608398684
1983	15.790172642762284
1984	15.336800710389445
1989	19.026752767527675
1991	22.933930571108625
1993	24.193548387096776
1995	26.35612282261861
1997	15.826330532212884
1998	19.93319813909102
1999	24.79851208927464
2000	25.832707237665915
2001	25.597310601512785
2002	28.76057374034572
2003	24.62423212651941
2006	20.18348623853211
2007	19.135634683337866
2008	20.16990956426418
2009	18.16785365172462
2010	17.92740371293987
2011	20.786516853932586