Year	Percent
1970	43.70266
1971	41.53678
1972	34.83473
1973	33.77768
1974	29.4836
1975	26.61152
1976	29.90375
1977	45.78614
1978	51.3629
1979	49.27266
1980	41.81179
1981	44.43884
1982	48.18627
1983	50.27028
1984	51.21214
1985	60.63912
1986	69.15272
1987	74.02558
1988	70.84686
1989	72.47588
1990	64.71646
1991	65.91495
1992	57.83806
1993	63.5274
1994	65.20537
1995	63.00058
1996	61.34398
1997	56.59758
1998	51.80316
1999	54.04896
2000	55.32424
2001	61.05639
2002	69.80636
2003	68.57385
2004	65.33412
2005	58.5006
2006	56.91087
2007	55.69892
2008	50.61298
2009	54.92345
2010	53.52545
2011	51.87086
2012	58.55742
2013	58.071
2014	57.46063
2015	64.86766
2016	69.49895