Year	Percent
1977	53.71531
1978	52.12828
1979	57.30586
1980	68.87755
1981	64.02484
1982	57.21815
1983	65.45204
1984	60.66603
1985	57.25782
1986	57.89464
1987	64.92146
1988	64.47403
1989	64.50949
1990	63.41386
1991	62.87868
1992	54.53666
1993	56.38567
1994	51.56575
1995	57.45381
1996	60.6375
1997	54.96498
1998	52.93726
1999	52.68442
2000	59.20977
2001	52.49416
2002	53.10019
2003	54.9669
2004	48.08367
2005	51.5732
2006	50.40568
2007	51.38216
2008	59.13892
2009	50.79942
2010	52.10201
2011	49.68979
2012	47.91276
2013	48.2072
2014	58.74228
2015	59.02585
2016	56.52908