Year	Percent
1975	0.71394
1976	0.31515
1977	0.22902
1978	0.47014
1979	0.87374
1980	1.49962
1981	1.48029
1982	2.34275
1983	4.72378
1984	3.61279
1985	6.74073
1986	4.69569
1987	3.52111
1988	5.07207
1989	4.66231
1990	4.19575
1991	4.50807
1992	5.23605
1993	5.32235
1994	5.4033
1995	6.09376
1996	5.58993
1997	6.53068
1998	8.54937
1999	10.15651
2000	7.49776
2001	8.16107
2002	7.73667
2003	5.4598
2004	3.67146
2005	5.72344
2006	3.05795
2007	5.90437
2008	2.23121
2009	2.59627
2010	2.06968
2011	2.02224
2012	2.34632
2013	2.80244
2014	2.93417
2015	3.90881
2016	4.19039