Year	Percent
1972	8.9832
1973	9.34624
1974	8.60419
1975	8.78601
1976	9.04636
1977	8.92465
1978	9.52537
1979	9.69649
1980	9.69653
1981	9.99523
1982	9.25278
1983	10.66742
1984	10.61847
1985	12.61946
1986	14.46931
1987	15.60795
1988	15.43889
1989	16.77351
1990	15.7536
1991	15.81994
1992	16.0651
1993	14.92254
1994	15.14791
1995	15.90836
1996	16.34986
1997	15.6686
1998	15.8349
1999	16.1044
2000	16.23226
2001	15.85784
2002	15.00371
2003	14.62739
2004	14.96262
2005	15.65864
2006	16.12145
2007	16.72491
2008	13.25736
2009	11.00744
2010	12.96646
2011	12.44777
2012	12.23833
2013	13.99444
2014	14.25247
2015	14.43058
2016	13.84774