Year	Percent
1977	14.88261
1978	20.17746
1979	20.97865
1980	21.11501
1981	22.74214
1982	14.50037
1983	5.07025
1984	5.51311
1985	7.04596
1986	5.01175
1987	4.68751
1988	4.48638
1989	6.40878
1990	9.25386
1991	11.23971
1992	7.22193
1993	5.94272
1994	5.42032
1995	5.11389
1996	2.78087
1997	7.06492
1998	11.30713
1999	10.71635
2000	6.85424
2001	7.90626
2002	6.94002
2003	12.91832
2004	8.56787
2005	8.22465
2006	20.62564
2007	21.28316
2008	12.57283
2009	11.5915
2010	8.77712
2011	6.70637
2012	5.27277
2013	5.6053
2014	3.06221
2015	5.74452
2016	5.75813
2017	5.39544