Year	Percent
1981	49.0608
1982	47.95323
1983	46.90888
1984	61.00025
1985	54.7311
1986	78.95482
1987	65.91055
1988	56.82115
1989	58.18043
1990	56.31669
1991	59.20022
1992	56.60294
1993	59.53003
1994	50.87301
1995	49.18447
1996	39.65474
1997	39.87325
1998	38.51889
1999	40.21083
2000	35.4721
2001	35.21263
2002	32.73706
2003	32.21421
2004	37.2785
2005	27.9998
2006	36.45433
2007	32.3717
2008	17.15638
2009	40.35724
2010	35.58453
2011	47.30379
2012	53.97335
2013	40.55176
2014	48.67949
2015	59.51732
2016	55.44426