Year	Percent
1981	21.63417
1982	28.40066
1983	49.23426
1984	58.53335
1985	62.84509
1986	56.0388
1987	62.02151
1988	54.96224
1989	55.15274
1990	56.23508
1991	56.78109
1992	52.98915
1993	50.63228
1994	48.76905
1995	49.77656
1996	53.50251
1997	45.92477
1998	46.87463
1999	55.39928
2000	61.82433
2001	73.23395
2002	80.34565
2003	95.14601
2004	95.17147
2005	86.15928
2006	72.70594
2007	66.09103
2008	59.21782
2009	57.18792
2010	56.0296
2011	57.18246
2012	63.97908
2013	63.37344
2014	60.31503
2015	62.86874
2016	58.47131