Year	Percent
1970	5.54262
1971	6.27785
1972	6.78294
1973	11.23328
1974	9.79733
1975	8.87257
1976	9.35335
1977	16.98169
1978	12.52711
1979	14.07747
1980	18.25918
1981	22.56564
1982	26.1186
1983	30.36341
1984	27.35768
1985	29.68552
1986	26.49297
1987	31.25471
1988	33.88204
1989	27.19825
1990	24.66163
1991	20.98603
1992	17.37287
1993	15.57351
1994	11.31928
1995	9.49798
1996	7.88876
1997	7.68934
1998	8.76629
1999	10.85842
2000	11.32708
2001	11.01886
2002	11.37955
2003	11.141
2004	9.66869
2005	9.92327
2006	12.26299
2007	11.39159
2008	11.30939
2009	18.25485
2010	18.73692
2011	23.14927
2012	19.41512
2013	19.29179
2014	20.09032
2015	20.89425
2016	19.5977