Year	% of total
1971	78.42688872589206
1972	77.87250658943738
1973	77.47333851051343
1974	74.78878276725356
1975	77.30482146459552
1976	77.90269432060477
1977	78.96560257362039
1978	82.61561009074184
1979	82.23089200212804
1980	80.63732827728437
1981	78.80492773304879
1982	77.294921875
1983	75.42681538811746
1984	77.00522006412464
1985	77.50858311621904
1986	78.97137009765756
1987	79.88818951475054
1988	79.98019111901836
1989	79.75581812896496
1990	79.5920601093248
1991	81.52886921232245
1992	82.41531632962943
1993	81.68342280942606
1994	80.32189777483315
1995	79.51263699085438
1996	81.12049174257572
1997	81.21821869761807
1998	80.73113490364025
1999	82.11289858193265
2000	82.12597124223116
2001	79.86169679036888
2002	80.86235705770407
2003	82.69464164688827
2004	81.4863340264724
2005	81.70185077501554
2006	82.49361294703264
2007	82.84347871131304
2008	80.28994703195819
2009	80.2483727723448
2010	79.4010250633517
2011	81.17400280263327
2012	77.85989296917066
2013	77.4244665797368
2014	74.82288736962218
2015	72.96207597398976