Year	Percent
1976	16.21302
1977	13.82806
1978	13.80296
1979	15.11354
1980	15.6386
1981	17.6651
1982	15.6005
1983	15.78205
1984	16.52467
1985	18.35837
1986	17.89929
1987	15.69599
1988	16.47239
1989	15.81639
1990	16.25743
1991	18.08495
1992	18.15235
1993	18.78971
1994	19.50882
1995	22.66848
1996	23.7501
1997	24.34973
1998	25.83638
1999	27.13097
2000	29.0183
2001	28.08582
2002	30.26632
2003	27.40272
2004	14.79274
2005	16.39591
2006	16.23768
2007	16.08185
2008	15.63053
2009	14.02832
2010	14.01838
2011	13.7074
2012	14.24146
2013	12.62217
2014	12.15374
2015	11.82216
2016	11.35302