Year	% of total
1971	59.899342757440266
1972	60.85957397582034
1973	61.324662044371415
1974	61.43695948517895
1975	64.43581417337543
1976	65.07885893973395
1977	67.47934390251949
1978	69.63723212178148
1979	69.65960606798824
1980	69.0747294923113
1981	68.38124886606067
1982	68.87318570139658
1983	69.60648100892143
1984	71.16390607489605
1985	71.56748105753616
1986	72.2246058893174
1987	73.23571056446042
1988	74.23521668272056
1989	74.31739394657681
1990	75.709160650649
1991	74.83196759859408
1992	75.4319836058588
1993	76.46878728715308
1994	77.0450401308995
1995	78.42785838465906
1996	78.9858756104578
1997	78.93511417044706
1998	78.99403588382211
1999	79.40000839610121
2000	79.84135583760963
2001	80.19740226743181
2002	81.202125230752
2003	83.2297577410762
2004	84.79645465096635
2005	85.87273599928993
2006	86.82834221821925
2007	87.40785733238019
2008	87.22405181821021
2009	87.63569469284496
2010	88.25519867320388
2011	88.8983629317114
2012	88.41916220675373
2013	88.23749256856516
2014	87.67043076818535