Year	% of total
1960	85.61042089546577
1961	87.61714451333104
1962	89.31098023879356
1963	89.16118114620792
1964	90.11980938700768
1965	90.05268689030589
1966	90.5498640135678
1967	91.62898255205472
1968	92.43561267997363
1969	93.30522622813245
1970	93.31802377874833
1971	93.46442774222035
1972	93.73671180088743
1973	94.54555308918347
1974	93.68373786509898
1975	93.16201775845066
1976	93.92315188490858
1977	93.0277292510405
1978	93.49310257347769
1979	93.84406981323497
1980	93.73038865548506
1981	93.35108724122307
1982	92.58894558045996
1983	92.52218785314437
1984	91.61572111307194
1985	91.81477521491752
1986	91.45783236568886
1987	93.38343377293097
1988	92.9048437377345
1989	93.29463061557998
1990	93.43818883146562
1991	92.89537207529075
1992	92.58124189283532
1993	92.2702900571247
1994	92.08793744899538
1995	93.02465206686588
1996	92.61465540907994
1997	92.44346417646835
1998	92.28589095434627
1999	91.8413718480898
2000	91.73009539319074
2001	91.40342478836986
2002	91.0358673382802
2003	90.21611169609193
2004	90.40624236209705
2005	89.80144618009906
2006	89.19087872196356
2007	88.18304312073485
2008	86.84215310440152
2009	84.85132566692076
2010	84.6287740206212
2011	84.4647972084689
2012	82.20135574290676
2013	79.96433458668163
2014	78.5864226219386
2015	79.94845473549468