Year	% of total
1960	12.89889330611368
1961	18.071654373024238
1962	18.956559703121588
1963	10.136309225006759
1964	17.919799498746865
1965	19.880847308031775
1966	14.07680670930757
1967	23.117644162111585
1968	22.752177424636006
1969	19.605657621646554
1970	21.71820329289736
1971	21.737436063976617
1972	23.042037841419422
1973	18.86862278614856
1974	16.157150706828514
1975	20.71670442641721
1976	17.865426634545354
1977	19.75207414040501
1978	20.748209343968746
1979	22.209487789270604
1980	30.0075073700401
1981	34.55034728535583
1982	39.42170457949359
1983	42.66757960789752
1984	41.848847645335546
1985	44.11345598127642
1986	43.230027763047076
1987	41.82088291630846
1988	31.675373780523003
1989	41.12703804347826
1990	40.11943970477362
1991	38.588294593179924
1992	41.569878749202296
1993	40.77998443119166
1994	38.91374874146996
1995	40.507620957027946
1996	31.534623482248435
1997	33.823428338805265
1998	32.66215769008025
1999	36.64841597963437
2000	36.6004137225524
2001	30.778274058532524
2002	34.3689692685387
2003	29.51852413208816
2004	29.033948787646572
2005	27.904092314602085
2006	22.99801747061729
2007	24.544541957798693
2008	16.069625504054947
2009	12.655677718428473
2010	8.823746312684367
2011	15.478865171352815
2012	19.048315654108634
2013	14.685640178365222
2014	16.47396426246322
2015	18.962389125676765