Year	% of total
1960	100
1961	100
1964	100
1965	100
1966	100
1967	100
1968	100
1969	100
1970	100
1971	100
1972	100
1973	100
1974	100
1975	100
1976	100
1977	100
1978	100
1979	100
1980	100
1981	100
1982	100
1983	100
1984	100
1985	100
1986	100
1987	100
1988	100
1989	100
1990	44.775999999999996
1991	34.71946808510638
1992	31.81012048192771
1993	18.083835616438357
1994	46.542692307692306
1995	45.4708
1996	43.72192307692308
1997	50.87549549549549
1998	49.53666666666666
1999	47.79122950819672
2000	47.37893805309734
2001	46.85611111111111
2002	45.58046728971963
2003	39.970299999999995
2004	39.63323232323233
2005	37.75920792079208
2006	38.122277227722776
2007	38.43298076923077
2008	40.62460784313725
2009	35.64186915887851
2010	36.67
2011	36.669999999999995
2012	49.12396226415095
2013	51.574580645161284
2014	18.71697916666667
2015	22.42922330097087
2016	26.235447154471547