Year	% of total
1971	61.64199192462988
1972	59.28753180661578
1973	57.177322074788904
1974	55.27522935779816
1975	53.551912568306015
1976	52.7542372881356
1977	52.00411099691675
1978	51.29740518962076
1979	50.63045586808923
1980	50
1981	49.403122130394856
1982	48.837209302325576
1983	48.29991281604185
1984	47.7891156462585
1985	49.00398406374502
1986	51.38339920948617
1987	52.10727969348659
1988	53.76344086021505
1989	51.369863013698634
1990	56.317689530685925
1991	57.03422053231939
1992	57.48987854251012
1993	60.18099547511312
1994	59.74025974025974
1995	61.73913043478261
1996	58.68544600938967
1997	55.44041450777202
1998	60
1999	55.376344086021504
2000	52.57731958762887
2001	52.475247524752476
2002	53.70145631067961
2003	55.814839508524614
2004	56.88799890775043
2005	57.31494413407822
2006	56.25139291285938
2007	61.701435673465596
2008	60.62486533074768
2009	59.16599611871065
2010	61.85376661742984
2011	68.65702694268178
2012	70.18091079226451
2013	75.82369626881955
2014	72.58920096041098
2015	72.79609812914028