Year	% of total
1960	94.13454680133336
1961	94.09571954319732
1962	94.21763356720116
1963	94.42413857295968
1964	94.53739930247939
1965	94.52379554232209
1966	94.43048498457715
1967	94.56634525412176
1968	94.56557653806482
1969	94.63801786260352
1970	94.54807463236827
1971	94.10380572113877
1972	93.81867404796564
1973	93.84281226142556
1974	93.17677008009404
1975	92.38051128085422
1976	92.42109056011745
1977	91.76886536293615
1978	91.15522835068587
1979	91.10874013895743
1980	90.5200389299574
1981	89.46395414757853
1982	88.63824589379855
1983	87.66297739083629
1984	86.7177986258281
1985	85.68500776308059
1986	84.98240712000509
1987	84.62463670138332
1988	84.31593958890416
1989	84.20775310537259
1990	83.53234741218229
1991	83.00683120839128
1992	82.86645791621875
1993	82.68605773156068
1994	82.64126690074367
1995	82.29607638760275
1996	82.32527573606127
1997	82.67672581217559
1998	82.4410231662649
1999	82.33440919310529
2000	82.3107717057543
2001	82.57116384455566
2002	82.54052142973026
2003	82.76916033821068
2004	82.38486464930753
2005	82.14809474710648
2006	81.84983694619933
2007	82.06535961973951
2008	81.55278410335892
2009	80.7800899591913
2010	80.61930746862132
2011	80.99242272844697
2012	81.03145232980582
2013	80.52744996446667
2014	80.16115894205397
2015	79.6762980161753