Year	Percent
1980	1.47677
1981	1.13887
1982	2.60721
1983	15.8636
1984	6.25662
1985	7.54311
1986	7.34696
1987	11.8319
1988	7.92378
1989	22.04276
1990	23.37122
1991	10.2192
1992	5.46109
1993	5.51085
1994	5.52952
1995	6.83029
1996	11.03525
1997	5.50624
1998	8.74742
1999	14.80496
2000	22.88023
2001	19.13575
2002	16.51177
2003	16.23098
2004	11.09744
2005	17.12077
2006	17.355
2007	19.95293
2008	24.07576
2009	18.07926
2010	16.49162
2011	14.55509
2012	12.58324
2013	14.05672
2014	19.28734
2015	15.04551
2016	9.28477
2017	13.39647