Year	% of total
1971	60.99230231409001
1972	60.49625867882267
1973	68.67498721887809
1974	66.88046153695082
1975	68.99199780019381
1976	68.14689311917854
1977	68.03385095277794
1978	66.7440107680042
1979	70.60117387533917
1980	72.7876235190309
1981	74.29706091197302
1982	77.06760675441836
1983	80.95036019615158
1984	82.69908904308772
1985	84.41533470548735
1986	83.98558386682929
1987	83.28524510442111
1988	84.67587922468076
1989	84.65910230636467
1990	86.3700032782701
1991	87.12659781654645
1992	87.09205357801663
1993	87.57977972449663
1994	88.99377585918428
1995	89.43309977391591
1996	89.3495852711791
1997	89.85276071678047
1998	90.30515147925911
1999	91.15271572014618
2000	92.16478922090967
2001	91.6553110723513
2002	92.12158071214405
2003	91.19088618993867
2004	91.57249462617753
2005	88.50698700791774
2006	88.31381834735498
2007	88.52210216211941
2008	91.86313837449428
2009	91.28958870874197
2010	90.96350685053768
2011	91.06386168485673
2012	91.03758292838613
2013	89.43669821407812
2014	89.27101804508068
2015	88.94310832261777