Year	% of total
1960	26.44087553425722
1961	30.706420883335394
1962	32.90083410565338
1963	36.32849700296902
1964	36.10776035383997
1965	28.18048691195314
1966	27.568325753389722
1967	27.934350132625994
1968	29.68263355016755
1969	37.12644121389735
1970	29.17118093174431
1971	41.67080348911425
1972	41.27571305099395
1973	38.698408591020836
1974	32.94417003442599
1975	32.181604786305215
1976	41.8011138542803
1977	33.594084869267036
1978	34.172041298404864
1979	30.51720277632659
1980	30.170673076923077
1981	25.775221322728783
1982	25.684858529655497
1983	25.652816163156388
1984	28.718527230396273
1985	27.06552055232957
1986	26.250085271846647
1987	25.58364192561584
1988	23.352509917132235
1989	25.89156749059099
1990	33.68833171048361
1991	34.839879635718695
1992	27.46951280562286
1993	25.81417531291974
1994	29.084070541728234
1995	29.36315198086194
1996	32.756561018404454
1997	31.811080183173207
1998	30.01967447683778
1999	29.043994926230056
2000	27.210475331529544
2001	30.453436389539355
2002	30.590056996013576
2003	38.79202024200906
2004	35.323174275198554
2005	35.908012467629135
2006	33.8117715056353
2007	30.61007536691789
2008	30.02680965147453
2009	27.917847879848
2010	32.868666647039774
2011	33.380973792394656
2012	24.30213942657546
2013	20.835011618900076
2014	17.721046481433394
2015	22.222042323073683