Year	Percent
1980	0.28411
1981	0.09982
1982	0.16103
1983	1.89253
1984	3.21085
1985	2.69191
1986	3.34018
1987	4.57899
1988	4.24235
1989	3.98312
1990	3.18218
1991	3.1756
1992	7.91581
1993	14.71742
1994	15.78431
1995	17.28275
1996	16.61115
1997	13.76172
1998	9.84428
1999	13.39528
2000	40.76717
2001	11.97494
2002	9.76774
2003	7.93096
2004	21.686
2005	18.67949
2006	24.58323
2007	32.08824
2008	26.02998
2009	27.07048
2010	43.05099
2011	38.59179
2012	33.55402
2013	30.22467
2014	48.34021
2015	25.37786
2016	23.5452
2017	29.55482