Year	Percent
1983	41.94831
1984	40.39015
1985	36.70987
1986	33.78821
1987	36.25429
1988	36.20735
1989	37.10764
1990	39.38494
1991	41.20477
1992	39.97996
1993	39.6805
1994	40.64204
1995	41.80084
1996	43.45578
1997	44.32896
1998	45.22777
1999	43.36006
2000	41.96907
2001	47.8935
2002	47.74533
2003	43.74957
2004	44.62762
2005	46.54106
2006	46.94356
2007	46.79914
2008	48.06074
2009	47.65212
2010	42.77587
2011	43.91342
2012	43.59374
2013	42.63568
2014	41.92834
2015	40.04786
2016	39.2932
2017	39.37126