Year	% of total
1971	81.53386454183267
1972	86.3541468969444
1973	86.31744919411352
1974	84.53231433792989
1975	83.9404978749241
1976	83.57192494788048
1977	85.97014925373134
1978	85.24280999528524
1979	88.44926611359286
1980	89.00790869956953
1981	89.7872340425532
1982	89.92052023121387
1983	89.72472299168976
1984	89.74859653404931
1985	89.96639068776129
1986	90.1183970856102
1987	90.60545869197381
1988	90.24205748865356
1989	90.89835291029596
1990	87.45340788072417
1991	86.52525100022646
1992	72.56890275611025
1993	69.28740229049264
1994	69.35227747597158
1995	71.28180431816358
1996	70.20247809005741
1997	77.88067298176163
1998	74.48402601074356
1999	66.78857300579631
2000	57.06492815327302
2001	56.71612523694359
2002	33.87476909357284
2003	29.07653383934219
2004	29.416656006140464
2005	36.84004692999609
2006	45.33972918817172
2007	40.9328188833409
2008	44.13145539906103
2009	38.60381188677117
2010	39.52980398919354
2011	44.47072072072072
2012	45.08356848274365
2013	48.34378265412748
2014	45.936176804709284
2015	45.96805993690852