Year	Percent
1971	41.38788
1972	43.55192
1976	53.83832
1977	56.76372
1978	60.32235
1980	59.9173
1981	62.08632
1982	64.59206
1983	66.99988
1984	69.32609
1988	50.40957
1991	52.33466
1992	48.65964
1993	56.12353
1994	47.35751
1999	34.89141
2002	42.73933
2007	55.4785
2008	60.55133
2009	63.15653
2010	63.68167
2011	65.61438
2012	70.9484
2013	69.81462
2015	69.9541