Year	% of total
1971	86.33651551312649
1972	86.64027709054923
1973	86.09967992684042
1974	86.24616732369688
1975	79.59434542102028
1976	77.59530791788856
1977	76.28094415659183
1978	74.90239821528165
1979	76.67258732978094
1980	76.0143198090692
1981	76.06888361045131
1982	77.96954314720811
1983	74.04773996952768
1984	87.47720364741642
1985	87.77506112469437
1986	88.3855981416957
1987	89.43396226415095
1988	89.62315674494812
1989	87.79811425402107
1990	92.43287225386493
1991	93.26424870466322
1992	95.52388097024256
1993	94.75072540226853
1994	94.49214659685865
1995	94.83616400754846
1996	94.12056972507453
1997	94.0687450039968
1998	95.07716049382717
1999	95.1732486003934
2000	95.15591886164093
2001	96.54447115384616
2002	97.75021632535334
2003	97.48110831234257
2004	96.71608701676597
2005	96.30827270277553
2006	96.05245550649003
2007	95.03002001334224
2008	93.86068476977569
2009	92.63301500682128
2010	92.31481481481481
2011	91.2734768666972
2012	89.07584128578604
2013	90.15777610818934
2014	90.20368574199806
2015	89.73799126637554