Year	Percent
1980	30.65547
1981	30.59004
1982	29.48365
1983	23.72985
1984	18.8379
1985	11.24266
1986	11.85396
1987	31.39181
1988	40.07506
1989	39.45276
1990	39.96689
1991	32.5085
1992	43.38384
1993	45.38957
1994	47.79186
1995	34.57932
1996	27.69704
1997	22.73333
1998	20.93062
1999	26.4402
2000	30.34007
2001	37.04691
2002	46.76528
2003	49.98778
2004	51.79474
2005	54.26299
2006	63.16608
2007	58.31083
2008	57.94795
2009	54.17467
2010	74.84559
2011	75.5171
2012	86.30293
2013	88.16397
2014	80.77925
2015	79.38353
2016	77.48097
2017	84.4847