Year	Percent
1960	16.11571
1961	16.5992
1962	19.1057
1963	14.20119
1964	13.88889
1965	11.25828
1966	8.4127
1967	5.17928
1968	6.47249
1969	6.46688
1970	5.46379
1971	5.46117
1972	6.54596
1973	7.30769
1974	8.76289
1975	9.76526
1976	13.65217
1977	12.41535
1978	13.87205
2002	12.33332
2003	16.84567
2004	18.7923
2005	21.56821
2006	23.35623
2007	19.86494
2008	18.86967
2009	17.89225
2010	17.86878
2011	16.55824
2012	16.8139
2013	17.23174
2014	18.05415
2015	19.36945
2016	17.70662