Year	Percent
1970	44.39103
1971	44.81132
1972	45.45455
1973	45.92145
1974	46.51852
1975	47.09302
1976	47.64622
1977	48.31933
1978	48.96836
1979	49.66262
1980	50.19868
1981	50.91146
1982	51.6624
1983	52.38693
1984	53.08642
1985	53.69697
1986	54.46961
1987	55.33411
1988	56.10599
1989	56.9161
1990	57.74805
1991	58.6169
1992	59.39525
1993	60.42553
1994	61.25654
1995	62.16495
1996	63.21138
1997	64.06406
1998	65.05429
1999	65.92016
2000	66.69866
2001	67.61364
2002	68.41121
2003	69.18819
2004	69.94536
2005	70.68345
2006	71.4032
2007	72.10526
2008	72.70364
2009	73.43616
2010	74.00508
2011	74.70687
2012	75.31069
2013	75.83948
2014	76.49919
2015	77.06496