Year	% of total
1971	72.0215089900857
1972	70.53117048346056
1973	71.6066066066066
1974	71.68774051676745
1975	73.03941215764863
1976	73.18089944416371
1977	69.85507246376812
1978	70.65267001369237
1979	72.35535405872193
1980	69.88336157910477
1981	74.36755952380952
1982	74.01269393511988
1983	75.89402733570493
1984	73.98622800306043
1985	77.46676575014449
1986	77.6953969725054
1987	77.66671426531487
1988	76.91115702479338
1989	76.54258031616521
1990	75.8183661645423
1991	79.35368043087972
1992	73.83782959914647
1993	79.67990275526742
1994	80.34161099205849
1995	79.41650148662042
1996	77.13640574339973
1997	73.56104084248064
1998	74.30955585464334
1999	76.33403361344537
2000	81.18911318670283
2001	84.73385311387044
2002	82.06341263703771
2003	80.84976443901589
2004	72.25314368171512
2005	70.90081963998588
2006	72.01915344688939
2007	65.31355450870335
2008	58.71106999691643
2009	59.190986668286314
2010	55.84285316244079
2011	55.036585676771274
2012	53.42640546423478
2013	51.27798464579598
2014	48.547872107772385
2015	49.14095044662287