Year	Percent
1970	7.44947
1971	9.31239
1972	6.19982
1973	7.3661
1974	11.58128
1975	16.39854
1976	17.83077
1977	21.95061
1978	25.08883
1979	30.78025
1980	27.38156
1981	29.67023
1982	26.49779
1983	26.54559
1984	21.27733
1985	21.06736
1986	24.85079
1987	30.185
1988	26.93339
1989	27.9917
1990	29.88077
1991	32.88977
1992	34.04721
1993	48.64247
1994	66.89968
1995	58.4321
1996	59.26792
1997	62.6209
1998	59.05426
1999	72.35356
2000	80.35306
2001	64.95587
2002	66.18815
2003	67.54049
2004	44.41
2005	28.98615
2006	28.2922
2007	24.84684
2008	20.7422
2009	21.13628
2010	20.94238
2011	19.81473
2012	19.56569
2013	23.6673
2014	17.98682
2015	15.31686
2016	17.57859