Year	Percent
1977	52.70592
1978	59.78228
1979	57.56407
1980	56.15332
1981	51.99665
1982	51.69939
1983	52.03975
1984	51.20668
1985	50.69711
1986	49.85045
1987	49.4185
1988	48.47692
1989	49.87875
1990	51.25818
1991	53.62751
1992	55.17293
1993	61.18014
1994	62.2273
1996	72.85516
1999	95.22665
2000	96.27847
2001	97.65063
2002	97.88513
2003	98.0931
2004	99.05979
2005	96.60106
2006	93.58761
2007	93.032
2008	94.08937
2009	95.80027
2010	95.90156
2011	96.37577
2012	97.13829
2013	96.59358
2014	95.32056
2015	95.53907
2016	96.61219