Year	Percent
1981	1.15347
1982	4.40343
1983	7.75514
1984	16.22475
1985	15.65364
1986	12.61914
1987	16.23097
1988	17.03078
1989	11.45862
1990	9.08401
1991	14.74222
1992	18.85175
1993	12.35302
1994	14.33358
1995	11.15488
1996	7.68892
1997	10.52934
1998	17.00435
1999	16.27966
2000	11.43833
2001	8.17484
2002	11.85923
2003	7.26372
2004	7.93066
2005	9.57642
2006	6.42695
2007	4.97489
2008	4.24749
2009	5.69317
2010	5.55661
2011	4.94699
2012	4.5675
2013	4.63139
2014	4.77427
2015	6.20824
2016	5.79478