Year	Percent
1960	6.55223
1961	5.48745
1962	4.79164
1963	7.30595
1964	7.06658
1965	10.90893
1966	33.47358
1967	36.96173
1968	38.20551
1969	38.65259
1970	36.92994
1971	53.84223
1972	37.68312
1973	26.30737
1974	34.43171
1975	38.31465
1976	38.92298
1977	33.24813
1978	28.38753
1979	28.86087
1980	44.54198
1981	44.09514
1982	64.3664
1983	64.77348
1984	64.67411
1985	64.6829
1986	61.00748
1987	60.73398
1988	58.63686
1989	58.16371
1990	55.92285
1991	55.85342
1992	53.1469
1993	53.46143
1994	53.95509
1995	53.20217
1996	54.62738
1997	56.4249
1998	55.06082
1999	53.30818
2000	51.31881
2001	48.27103
2002	49.10612
2003	49.23618
2004	48.7011
2005	48.87779
2006	47.45328
2007	52.54169
2008	50.95348
2009	56.65934
2010	56.45019
2011	54.70569
2012	56.09885
2013	56.62815
2014	54.43503
2015	52.91261
2016	52.60035