Year	Percent
1971	43.96397
1972	38.831
1973	48.81683
1974	42.36195
1975	54.90043
1976	43.16632
1978	61.34091
1981	42.2255
1982	42.00511
1983	37.82009
1986	48.34745
1987	36.2443
1988	37.30545
1989	37.84247
1990	41.65808
1991	36.62613
1992	29.7672
2004	30.13715
2005	32.74076
2006	32.17276
2008	44.29878
2009	46.83892
2010	50.58229
2011	51.53682
2012	53.65306
2016	50.9254