Year	Percent
1977	0.58964
1978	0.80937
1979	1.18306
1980	3.80225
1981	6.42734
1982	13.21694
1983	36.90737
1984	26.15869
1985	29.04444
1986	31.13683
1987	32.28517
1988	28.48007
1989	22.3751
1990	23.14536
1991	23.12187
1992	32.2986
1993	30.99862
1994	25.20433
2009	6.06869
2010	10.54691
2011	22.62583
2012	15.92509
2013	11.00871
2014	10.90891
2015	13.39788