Year	% of total
1960	34.65973534971645
1961	38.07167743857422
1962	41.55974087691654
1963	46.474760116812675
1964	49.68516231745026
1965	51.97983206020055
1966	53.92914864805836
1967	57.747469908377745
1968	59.41999700155789
1969	61.53384622286022
1970	65.44119049890298
1971	69.36439041436007
1972	71.69953204965688
1973	71.15009590472796
1974	69.41996548700557
1975	69.70931972301715
1976	70.99653029936255
1977	71.5607661693493
1978	72.13743245216882
1979	71.12816577129702
1980	66.60977922253825
1981	63.57877131113268
1982	63.01392741774513
1983	63.36355149880718
1984	60.47718975255093
1985	57.889044229282426
1986	59.08202264296073
1987	59.253186286417595
1988	59.18509593104088
1989	60.03218078449601
1990	60.33989831222084
1991	58.77262476710743
1992	60.748480138169256
1993	59.395512589441815
1994	59.77833705952156
1995	58.93514576352118
1996	58.48225563339319
1997	57.52366323392874
1998	57.987385281767956
1999	56.79385336524029
2000	55.89977961874973
2001	54.37755462917087
2002	52.99326478702867
2003	52.69581972067314
2004	51.79350989604406
2005	51.47400726631626
2006	50.17239519096668
2007	47.61065877882514
2008	47.86180973077387
2009	45.95563080611328
2010	44.23313992111272
2011	43.44422564491779
2012	42.88786994298127
2013	40.617063526052824
2014	39.86466880359397
2015	38.88882209056285
2016	37.78663826735759