Year	Percent
1980	30.68861
1981	34.52261
1982	33.21649
1983	36.93962
1984	38.24615
1985	43.20224
1986	43.46992
1987	42.62235
1988	45.89609
1989	48.15838
1990	36.72787
1991	39.20413
1992	52.93825
1993	45.83473
1994	45.67256
1995	49.90614
1996	45.38905
1997	37.28416
1998	36.06286
1999	47.78895
2000	41.81989
2001	44.53882
2002	41.94551
2003	44.94189
2004	52.50857
2005	57.63358
2006	64.5383
2007	71.21172
2008	72.30149
2009	50.60909
2010	53.02841
2011	58.69288
2012	63.97452
2013	65.0623
2014	65.95552
2015	63.95947
2016	59.66521
2017	64.79609