Year	% of total
1971	11.16399906532296
1972	9.998743675966235
1973	11.697220188123216
1974	9.363878882152928
1975	12.73816755546115
1976	15.130147222773878
1977	11.317553637524837
1978	12.291786249792594
1979	14.680820289166668
1980	11.987382005173364
1981	11.08387278029028
1982	11.34165105791565
1983	11.291295787614919
1984	9.885953792578375
1985	10.468186889799101
1986	9.451082203483837
1987	11.225644586209798
1988	14.448936633917809
1989	16.37721568718066
1990	14.883268090897413
1991	13.636429755349688
1992	14.327117400059223
1993	14.96722285882167
1994	17.44585492032387
1995	15.7211494762401
1996	16.95134436576082
1997	20.179489989858997
1998	17.892878683814622
1999	18.638341683191694
2000	17.510037592115545
2001	16.367145059720745
2002	17.751916231824126
2003	17.034007181948787
2004	17.64176856993323
2005	24.412474200078517
2006	26.696476437497623
2007	25.193539369944993
2008	27.645534992645427
2009	26.890640203407123
2010	24.557534715726323
2011	25.724426673473406
2012	23.731849181786682
2013	23.13228843902766
2014	23.046042932222868
2015	24.32496431662226