Year	% of total
1960	12.828947368421053
1961	14.061838204150783
1962	16.416129801956576
1963	18.90451832907076
1964	22.003593121738383
1965	23.56107988282796
1966	25.392886683209266
1967	27.539218293007178
1968	29.520113349350087
1969	33.93735152753992
1970	41.532934131736525
1971	46.07927003136584
1972	46.85508451094486
1973	47.65304491448666
1974	49.277003036072664
1975	46.85806063039551
1976	48.29229148904158
1977	48.73292465125259
1978	48.67348317643349
1979	45.21658559184618
1980	39.9555155932043
1981	40.534002738475586
1982	43.75279710321819
1983	43.47279146207848
1984	41.23819517313746
1985	41.10901793758702
1986	41.738782051282044
1987	39.61342990916003
1988	39.31272055116787
1989	39.91713875031707
1990	34.0927311038608
1991	29.074473639310693
1992	26.30688372936695
1993	48.07215017064846
1994	29.934833707025412
1995	32.4256939111355
1996	26.833169269887396
1997	21.973142214727375
1998	24.122901759240957
1999	25.72694356659142
2000	24.339469189937688
2001	22.853239497618016
2002	27.37432729773092
2003	25.146017957820003
2004	24.133181432810513
2005	27.00468253968254
2006	27.152423933020213
2007	24.23063283922463
2008	24.231665000999403
2009	26.9670002327205
2010	24.87182608695652
2011	20.834052748137708
2012	24.21097739361702
2013	25.131197890507284
2014	26.084934880416768
2015	26.47066905347953
2016	29.27274556780067