Year	% of total
1960	74.68165699548678
1961	72.25054337087532
1962	69.91441491946033
1963	67.44202170069678
1964	62.77547843927979
1965	58.694442512346114
1966	55.35726734053677
1967	52.96164869660161
1968	49.35510810058458
1969	45.246358755302424
1970	39.03727705286511
1971	33.27600253462478
1972	32.22623952465035
1973	32.60278313221198
1974	35.86440677966101
1975	31.54037901312431
1976	31.76510407852429
1977	30.704600764862672
1978	32.155581947743464
1979	33.617488625071914
1980	34.88088462476624
1981	37.29044085035924
1982	38.84954924041551
1983	36.074327981237595
1984	39.879647987756094
1985	38.999648999649
1986	35.08234119911599
1987	35.380512091038405
1988	33.03613841487923
1989	37.314451458795425
1990	34.9926603238496
1991	31.749990347490343
1992	29.938624588266716
1993	27.644870583961495
1994	28.480685813751087
1995	27.39127694859038
1996	25.363544579321896
1997	25.02513717421125
1998	24.785492839795662
1999	22.36835079213921
2000	24.801026603001365
2001	22.5213418962312
2002	20.99634551195309
2003	18.966803463203462
2004	18.44113138045957
2005	16.868001084892867
2006	16.541156925908883
2007	15.34256812314753
2008	15.226297577854671
2009	11.353829637804754
2010	13.043044049967126
2011	13.513836978131213
2012	12.376511162594777
2013	12.829375841010245
2014	13.092361357586512
2015	12.060269957983195
2016	11.193058736217134