Year	Percent
1972	50.40809
1973	52.85018
1974	56.29261
1975	58.06382
1976	58.72677
1977	61.87583
1978	67.35429
1979	67.08631
1980	67.47211
1981	69.51441
1982	71.40974
1983	73.02257
1984	75.58162
1986	77.57018
1998	57.83171
1999	55.44375
2000	54.0943
2002	53.21813
2004	64.23755
2005	67.97169
2006	76.50939
2007	79.78257
2008	83.56841
2009	78.40733
2010	99.93936
2012	86.37758
2013	77.59141