Year	% of total
1971	74.33596132913766
1972	74.77516253355412
1973	74.10581787301875
1974	71.72003827933246
1975	73.91198585843821
1976	74.4887716324312
1977	76.18250162186175
1978	79.5476862155474
1979	78.97628869778919
1980	77.85638046179818
1981	75.7567286334523
1982	74.61874883555485
1983	73.26653037793588
1984	73.9283666745619
1985	74.88824499893938
1986	75.64567681810148
1987	77.31227599553931
1988	77.27853264792155
1989	76.84550855048829
1990	77.32543925310536
1991	79.28297648696645
1992	80.26724984645753
1993	80.13753348267123
1994	79.1649578779205
1995	78.60187927083375
1996	80.18790455058884
1997	81.05787867639059
1998	80.57309783327419
1999	81.29809394202236
2000	81.21901109839885
2001	79.40612075564225
2002	80.54218344620384
2003	82.19668398903069
2004	81.35147694285354
2005	81.65391930950973
2006	82.20194900839782
2007	82.52523448763505
2008	80.2234522369789
2009	80.2142063598255
2010	79.65957672913083
2011	80.92094109288473
2012	77.9098316231875
2013	77.52252942286023
2014	75.22400292262955
2015	73.7742018361624