Year	Percent
1974	81.65869
1975	84.80066
1976	82.49186
1977	86.78778
1978	89.43612
1979	89.07216
1982	88.24298
1983	89.94343
1984	87.99769
1985	87.30878
1986	88.01454
1992	85.06589
1993	85.48781
1994	84.14008
1995	82.21659
1996	81.04882
1997	80.00917
1998	78.21516
1999	77.89719
2000	80.02228
2001	80.94874
2002	77.0257
2003	77.18227
2004	76.61347
2005	74.54941
2006	75.14376
2007	76.60806
2009	72.11214
2010	75.08468
2011	79.10672
2012	77.18895
2013	76.82791
2014	76.53651
2015	74.60345
2016	72.48705
2017	73.54284