Year	Percent
1971	34.58417
1972	38.90781
1973	36.5167
1974	28.31309
1975	13.86268
1976	10.8
1977	11.53049
1978	10.02603
1979	11.11185
1980	6.31117
1981	2.64258
1982	1.3
1983	2.49788
1984	1.24899
1985	1.51947
1986	1.56471
1987	0.61079
1988	0.71654
1989	0.34186
1990	0.45367
1991	0.75744
1992	1.36137
1993	1.86096
1994	2.60848
1995	2.77033
1996	2.14132
1997	3.20527
1998	3.33733
1999	2.99226
2000	3.94176
2001	4.08289
2002	6.01319
2003	4.22759
2004	7.43187
2005	9.44829
2006	12.03212
2007	39.29738
2008	34.7372
2009	47.26172
2010	43.92212
2011	41.80512
2012	42.40489
2013	38.16145
2014	48.54186
2015	42.00544
2016	33.77072