Year	Percent
1974	90.51571
1975	91.97197
1976	90.3995
1977	96.68525
1978	94.81836
1979	91.48078
1982	91.27849
1983	96.7598
1984	94.48622
1985	93.08162
1986	93.95994
1987	89.05647
1988	85.65986
1989	86.81167
1991	86.1209
1992	77.52729
1993	78.55791
1994	77.05877
1995	75.8749
1996	75.18636
1997	74.32317
1998	74.55818
1999	73.68524
2000	73.86442
2001	73.60816
2002	71.715
2003	71.43
2004	71.66574
2005	70.91237
2006	71.84689
2007	74.11153
2009	72.35516
2010	73.50528
2011	75.55413
2012	75.50813
2013	75.42048
2014	74.51747
2015	72.5297
2016	71.11082
2017	71.23757