Year	% of total
1960	58.60797144556812
1961	55.4724364138566
1962	53.38524767467013
1963	53.023394131641545
1964	48.66290018832392
1965	47.08085269829076
1966	42.93853913693256
1967	39.44398568676025
1968	36.358126244696514
1969	34.3206432556613
1970	35.141782407407405
1971	28.87576460662308
1972	27.84521012790394
1973	26.372889620284028
1974	28.91781521184278
1975	26.798355019213915
1976	24.444444444444446
1977	22.32731067771182
1978	22.34626180147997
1979	23.456569625528367
1980	27.152271452607962
1981	26.10570327301235
1982	26.249149081007484
1983	27.715857787810382
1984	30.922290938424307
1985	30.475296641415834
1986	27.25115269867101
1987	25.64933003111704
1988	26.804619826756497
1989	25.606450738582463
1990	26.96601166981294
1991	26.33636815123358
1992	22.10882434541356
1993	19.794186851211073
1994	19.9234671470235
1995	21.601614906832296
1996	20.453836671802776
1997	21.966597633136097
1998	19.11466986237823
1999	19.51274385408406
2000	21.88194081536282
2001	21.107794139302015
2002	20.99128874153092
2003	21.004237174321783
2004	20.115284960422166
2005	20.0617221930745
2006	20.863794871794873
2007	20.620440763615946
2008	20.26104340449597
2009	17.037148401117665
2010	18.639010863350485
2011	19.41194961183536
2012	18.906648748272158
2013	19.057245627376425
2014	18.41485884820132
2015	19.42377672209026
2016	17.973448493453226