Year	% of total
1971	77.65043113667271
1972	77.77281568852094
1973	76.72162938061963
1974	74.06739916817465
1975	76.08548404974694
1976	76.60933074199644
1977	78.24082485666719
1978	81.59645604429943
1979	80.81867409772394
1980	79.52211884063357
1981	77.25306819848473
1982	75.9637362881904
1983	74.44324406697827
1984	75.05840302107667
1985	76.10796791160858
1986	76.91632391115724
1987	78.59834407974644
1988	78.5994030568117
1989	78.01196662912224
1990	78.55436714806176
1991	80.43533324884262
1992	81.28125146988819
1993	81.009793171045
1994	79.95695365847052
1995	79.34811343164299
1996	80.80379888627493
1997	81.55341750339117
1998	81.04507984628005
1999	81.73904913362539
2000	81.60792668843096
2001	79.75776654871876
2002	80.87601790141503
2003	82.54186777801375
2004	81.67066515267041
2005	81.95644727174717
2006	82.46013474524399
2007	82.77635873776981
2008	80.46081464550896
2009	80.40874828216484
2010	79.84656029418383
2011	81.09914308022258
2012	78.0727106436394
2013	77.681047260583
2014	75.35700563405827
2015	73.87038286668474