Year	Percent
1980	7.63227
1981	9.5283
1982	11.3842
1983	11.59991
1984	11.68287
1985	3.45697
1986	7.02615
1987	17.01417
1988	21.42629
1989	21.00552
1990	22.06781
1991	21.72132
1992	23.9888
1993	24.87969
1994	20.41554
1995	29.7267
1996	18.02601
1997	17.38565
1998	21.2698
1999	36.25313
2000	33.13777
2001	24.72745
2002	32.60664
2003	25.70056
2004	21.54732
2005	19.02213
2006	17.99407
2007	15.13063
2008	17.25142
2009	14.68629
2010	18.2955
2011	25.66719
2012	47.38199
2013	54.46886
2014	55.36271
2015	45.32566
2016	38.30654
2017	35.55448