Year	Percent
1971	40.94535
1972	38.77994
1973	41.39825
1974	43.67853
1975	45.33723
1976	46.60378
1977	46.57063
1978	36.4857
1979	23.39937
1980	36.23226
1981	43.43716
1986	61.5839
1997	80.53463
1999	85.77159
2000	84.59291
2001	83.80893
2002	85.1422
2003	84.82831
2004	87.25781
2005	86.75021
2006	85.59207
2007	90.03416
2009	95.90022
2010	99.50827
2013	100.92949
2016	94.68839