Year	Percent
1970	9.40435
1971	9.75741
1972	10.79397
1973	11.6259
1974	12.11938
1975	12.58269
1976	11.74229
1977	12.18204
1978	14.30673
1979	14.71543
1980	11.67074
1981	12.71593
1982	14.29488
1983	14.48121
1984	12.58092
1985	11.82188
1986	12.12885
1987	15.71135
1988	14.81469
1989	17.26292
1990	17.32688
1991	17.53485
1992	18.98601
1993	20.12341
1994	19.57291
1995	16.80067
1996	11.78259
1997	13.89043
1998	14.69128
1999	16.11961
2000	15.53957
2001	15.57319
2002	15.804
2003	15.74171
2004	16.32302
2005	16.93976
2006	15.31648
2007	16.59737
2008	14.66325
2009	15.18052
2010	15.26723
2011	15.45606
2012	15.42385
2013	16.16927
2014	16.63596
2015	15.09783
2016	15.14867