Year	% of total
1971	54.32659092426263
1972	55.99395559116359
1973	57.241744941248264
1974	59.590864588966156
1975	59.044849513433626
1976	60.47183704702468
1977	61.07248629824195
1978	60.094389072649165
1979	61.039529104786475
1980	61.66794258459022
1981	62.74631139036173
1982	62.915208123879864
1983	63.21636499552569
1984	64.87049563920738
1985	66.03944637603487
1986	64.84127125409508
1987	65.04531648860564
1988	64.63855422337559
1989	64.32851168910932
1990	65.54204868529202
1991	65.16384772672902
1992	64.77291404142508
1993	66.2201984415535
1994	65.26233468514879
1995	65.00191122225273
1996	64.79455878481343
1997	63.7971315645635
1998	61.54662416174982
1999	60.52134670352326
2000	60.598699345049866
2001	56.87057846758245
2002	57.36977215493244
2003	56.08430550443209
2004	56.22407383692768
2005	56.98074999838199
2006	57.45494917373113
2007	56.43940986862079
2008	55.5509331021429
2009	55.71874632062542
2010	54.02405564106687
2011	54.87858257481787
2012	51.689289072413914
2013	49.30000239582179
2014	48.151561221309876
2015	45.39564409690815