Year	Percent
1980	27.35933
1981	25.75437
1982	26.21442
1983	22.76347
1984	18.35994
1985	11.46613
1986	12.02637
1987	31.38506
1988	37.29757
1989	38.64892
1990	36.06815
1991	44.15418
1992	54.18846
1993	50.23789
1994	51.75799
1995	56.92
1996	40.54543
1997	34.0772
1998	30.20072
1999	39.52037
2000	39.5645
2001	34.30052
2002	56.00572
2003	50.94531
2004	48.28029
2005	46.17729
2006	40.9849
2007	39.91219
2008	39.17347
2009	41.27723
2010	46.22133
2011	54.90777
2012	78.45367
2013	84.00663
2014	84.76333
2015	71.98986
2016	74.13914
2017	70.64032