Year	% of total
1971	67.3911030558475
1972	68.39802198810492
1973	70.10514830173192
1974	70.57855461043275
1975	70.63774952792127
1976	71.49518447450325
1977	72.05117944970519
1978	73.01919263837804
1979	73.2357316425456
1980	73.75268906156833
1981	73.73211123997275
1982	73.53322237579555
1983	71.93094454370816
1984	70.73506568007033
1985	70.39706381780132
1986	70.69380106313652
1987	70.35609659272568
1988	70.8221609086799
1989	70.99858407961521
1990	71.27240365223362
1991	71.67249939769447
1992	72.34395905854888
1993	72.16387438623407
1994	72.70926966240312
1995	72.33231944770834
1996	73.06415652787663
1997	73.50735840776292
1998	74.25637936759212
1999	74.16913344045491
2000	74.57433994701127
2001	74.89006727523602
2002	74.33637198205716
2003	73.65160385463271
2004	73.73270767531488
2005	73.59008989233241
2006	73.59486209493846
2007	72.89144696484985
2008	73.14614884897422
2009	72.96474896779537
2010	73.22674145773591
2011	73.43299714360808
2012	74.0880154906116
2013	74.08753461916663
2014	73.16127163123794
2015	87.88038849631673