Year	% of total
1971	64.8881239242685
1972	61.41078838174274
1973	73.06322350845949
1974	73.22253000923361
1975	79.23519736842105
1976	64.50020567667627
1977	80.80229226361033
1978	71.32915796798886
1979	71.48217636022514
1980	80.57090239410681
1981	56.51387213510254
1982	68.43546730571722
1983	69.69785860956293
1984	65.87954364552931
1985	71.40119760479043
1986	66.81303443494338
1987	65.966116234184
1988	53.9010989010989
1989	84.66973886328725
1990	89.88642509464574
1991	86.34146341463415
1992	89.9838738577316
1993	78.25518400896694
1994	89.77534052715373
1995	88.22348000730327
1996	86.34920634920636
1997	90.14648977335544
1998	88.75035690492052
1999	85.7548932023065
2000	90.8522163729305
2001	92.54081074748106
2002	91.12891686936615
2003	87.90574824494335
2004	83.48449868073878
2005	82.20767628681939
2006	84.6180411659069
2007	85.86934807218486
2008	88.39214645794641
2009	86.9534355479841
2010	88.11119219796988
2011	87.91038292062309
2012	85.523411176949
2013	83.43031159932568
2014	86.66062733552259
2015	88.36755702443517