Year	Percent
1977	1.35657
1978	2.87491
1979	3.5015
1980	3.20762
1981	2.9783
1982	2.69474
1983	2.32634
1984	2.43727
1985	2.18473
1986	2.6636
1987	4.79441
1988	4.89968
1989	3.56901
1990	4.44516
1991	4.60347
1992	4.48281
1993	4.93349
1994	4.00812
1995	3.50648
1996	2.89952
1997	3.1972
1998	3.7794
1999	3.09207
2000	3.19124
2001	3.83122
2002	4.11021
2003	4.00737
2004	3.50587
2005	2.858
2006	2.69512
2007	2.80146
2008	3.03697
2009	3.21559
2010	2.72686
2011	2.3167
2012	2.20976
2013	2.0564
2014	2.13086
2015	2.66287
2016	3.30474
2017	3.05254