Year	Percent
1971	16.71118
1972	23.21971
1973	7.83508
1974	28.33238
1975	30.5912
1976	6.3964
1977	4.36496
1978	9.53676
1979	2.5526
1980	1.50744
1981	0.75382
1982	1.04927
1983	0.51753
1984	0.44528
1985	0.42397
1986	0.54096
1987	0.47746
1988	0.21331
1989	0.80417
1990	1.461
1991	6.29158
1992	9.82953
1993	12.57593
1994	12.04454
1995	12.69559
1996	20.51225
1997	19.83821
1998	18.67948
1999	18.71577
2000	22.18883
2001	21.63887
2002	20.46494
2003	19.00833
2004	16.94417
2005	20.33343
2006	24.04386
2007	36.88863
2008	35.93664
2009	44.22226
2010	55.53289
2011	39.95776
2012	43.76781
2013	34.04227
2014	28.52134
2015	32.45169
2016	35.44868