Year	% of total
1960	85.44074708887621
1961	86.6094140073205
1962	87.40390522825355
1963	87.86942422229343
1964	89.08839987206701
1965	87.97762182751164
1966	87.48781591414595
1967	87.74547222489501
1968	88.49453945252145
1969	89.511758479888
1970	88.99204257987063
1971	90.19969369309229
1972	90.12373159462952
1973	89.77446241105375
1974	88.65248261131772
1975	88.39898888918214
1976	89.59968424417724
1977	88.1923619073637
1978	87.60895289985788
1979	87.0076277971248
1980	85.89521616401274
1981	83.96376022136376
1982	82.74158705788483
1983	82.44589222455637
1984	81.8351143304607
1985	81.04281229177755
1986	79.74839655694737
1987	79.5788581060508
1988	74.69315383406521
1989	76.54434927780457
1990	79.1323454283578
1991	79.12700715650539
1992	77.23721117428765
1993	77.0111424905957
1994	77.58570757509024
1995	77.98279868095946
1996	78.19818694350876
1997	78.41612404994794
1998	78.5155637093458
1999	76.60732844589133
2000	76.53529223461383
2001	76.89638903354617
2002	77.31087416751208
2003	78.14442930483148
2004	77.69929365819102
2005	77.03042942998188
2006	74.69833424034242
2007	72.62977853771083
2008	71.55486310268553
2009	69.83650771641395
2010	70.26705703172875
2011	69.15418339945117
2012	67.30250678634732
2013	66.25380350853943
2014	64.81315646614684
2015	65.66182198947268