Year	% of total
1960	99.54873646209387
1961	99.51091045899172
1962	99.57908369758782
1963	99.66555183946488
1964	99.68079673135854
1965	99.683303775019
1966	99.73892961140677
1967	99.75350029579964
1968	99.83773759851647
1969	99.87494315597999
1970	99.88014382740711
1971	99.87113402061856
1972	99.88334791484398
1973	99.87447698744771
1974	99.86887395508933
1975	99.86859395532196
1976	99.88297820469062
1977	99.90029006526468
1978	99.87266137721618
1979	99.85979829044366
1980	99.84681487016627
1981	99.77736173657846
1982	99.78926072662901
1983	99.57617566166194
1984	99.57657021877205
1985	99.59854515509195
1986	99.3307994672384
1987	99.10475092407339
1988	98.55005343783398
1989	97.46217241529673
1990	96.7362019859903
1991	96.93254891229991
1992	95.2306591190058
1993	94.7253782304115
1994	95.1328305978609
1995	88.18216442679145
1996	87.9063864730693
1997	82.40324946406409
1998	80.69710310607351
1999	77.69013360739979
2000	72.51823703991346
2001	74.12600386970234
2002	74.56410517473974
2003	80.55471354956047
2004	74.8095756256801
2005	70.67814379517739
2006	78.02065291267456
2007	71.76721945264015
2008	70.09230937295172
2009	70.16463733062145
2010	66.09541454377026
2011	57.537823951857845
2012	49.294811243933424
2013	51.98169415421812
2014	41.849987571464084
2015	31.89967872318375