Year	Percent
1960	7.02479
1961	8.09717
1962	9.34959
1963	16.86391
1964	18.05556
1965	21.4128
1966	18.57143
1967	14.20983
1968	15.21036
1969	14.98423
1970	11.94411
1971	16.1408
1972	18.10585
1973	14.74359
1974	14.84536
1975	14.2723
1976	14.86957
1977	14.82318
1978	13.87205
2002	65.2877
2003	94.34417
2004	87.13932
2005	77.46715
2006	74.08506
2007	58.35005
2008	55.07255
2009	42.19923
2010	44.94348
2011	44.19395
2012	39.1424
2013	49.75777
2014	45.77388
2015	48.80162
2016	49.02498