Year	Percent
1960	42.6944
1961	43.68763
1962	43.43744
1963	42.76632
1964	42.64339
1965	42.8994
1966	43.30446
1967	42.47567
1968	44.39392
1969	47.62224
1980	55.43561
1981	52.96439
1982	48.96184
1983	49.21559
1984	52.09847
1985	53.93996
1986	50.81874
1987	49.70742
1988	51.15525
1989	54.29518
1990	51.71728
1991	49.02154
1992	48.34218
1993	46.91189
1994	47.27783
1995	47.2227
1996	47.8567
1997	53.08895
1998	53.87311
1999	55.24322
2000	59.92196
2001	59.66523
2002	59.34905
2003	58.10496
2004	60.54414
2005	63.0071
2006	67.12499
2007	69.4414
2008	69.32864
2009	60.54446
2010	63.70345
2011	63.32934
2012	91.07564
2013	98.67193
2014	82.76348
2015	79.92615
2016	85.68504
2017	83.73206