Year	% of total
1971	65.06200566350942
1972	69.32649377790445
1973	68.28072589661993
1974	68.42715743891122
1975	68.83458355888949
1976	67.10199912447104
1977	68.51281379039129
1978	69.51563669872718
1979	69.7711128650355
1980	69.86696664384232
1981	68.7827886605381
1982	68.1543593904968
1983	66.63173979480462
1984	67.41124377322684
1985	68.37514444403027
1986	72.10329595650697
1987	73.44509000857225
1988	73.84284502605112
1989	76.23391478410065
1990	75.63055257584509
1991	74.95539334955393
1992	67.6329528897523
1993	72.24513083845535
1994	77.42036755294743
1995	75.28794830976683
1996	81.84816198514828
1997	70.5615962336061
1998	68.56137381116778
1999	78.79361076082387
2000	74.37449275362319
2001	73.19644583582708
2002	75.41405799032015
2003	77.72501665198426
2004	80.60701140409098
2005	79.07304765877983
2006	79.49781456337767
2007	80.4813124728379
2008	82.9543423075548
2009	71.82977829883288
2010	67.9876817447496
2011	80.12130153266126
2012	76.32904488434022
2013	70.96662731434824
2014	70.90613455805793
2015	64.95935783937291