Year	Percent
1960	11.74089
1961	12.54902
1962	14.38127
1963	14.88095
1964	15.36388
1965	15.56122
1966	10.8642
1967	12.04819
1968	12.07564
1969	13.58234
1970	12.21996
1971	12.79707
1972	16.07717
1973	14.26873
1974	13.65854
1975	14.46655
1976	17.91277
1977	11.89768
1978	17.25626
1979	22.10397
1980	21.00565
1981	19.29134
2007	49.1929
2008	49.98179
2009	41.76289
2010	39.4492
2011	44.1447
2012	38.67213
2013	35.8217
2014	35.61793
2015	40.38949
2016	42.2454