Year	Percent
1970	16.93563
1971	16.93796
1972	16.93794
1973	16.93516
1974	16.93155
1975	16.93551
1976	16.94965
1977	16.93781
1978	16.9213
1979	16.91347
1980	16.95533
1981	17.02036
1982	16.87858
1983	16.83876
1984	16.87434
1985	17.16463
1986	17.34546
1987	16.1697
1988	16.63967
1989	17.05222
1990	17.3576
1991	17.01741
1992	16.81331
1993	16.29366
1994	16.91459
1995	17.96093
1996	26.68553
1997	27.57883
1998	25.919
1999	25.39326
2000	25.53508
2001	24.86238
2002	23.70134
2003	22.50593
2004	22.03963
2005	21.52683
2006	22.20474
2007	22.527
2008	22.3865
2009	22.6047
2010	22.89361
2011	22.2583
2012	23.36719
2013	23.15031
2014	22.15208
2015	22.35381