Year	Percent
1971	9.48838
1972	10.24063
1973	13.44634
1974	6.58031
1975	4.4976
1976	22.19713
1977	8.81821
1978	16.63987
1979	0.65187
1980	0.72897
1981	1.64387
1982	1.03271
1983	1.43224
1984	2.74346
1985	1.91529
1986	3.8081
1987	5.0277
1988	6.07348
1989	7.14773
1990	2.48803
1991	2.27361
1992	2.15853
1993	2.11954
1994	1.74883
1995	2.52107
1996	5.81026
1997	6.85338
1998	3.90029
1999	4.75112
2000	6.03429
2001	9.52021
2002	7.99475
2003	8.31942
2004	13.16496
2005	13.65182
2006	38.19166
2007	36.98116
2008	39.40509
2009	34.9811
2010	37.62734
2011	40.10513
2012	35.63286
2013	26.84346
2014	26.9535
2015	28.11987
2016	40.33687