Korchnoi was a candidate for the World Championship on ten occasions ( 1962 , 1968 , 1971 , 1974 , 1977 , 1980 , 1983 , 1985 , 1988 and 1991 ) .
In all , Korchnoi was a candidate for the World Championship on ten occasions ( 1962 , 1968 , 1971 , 1974 , 1977 , 1980 , 1983 , 1985 , 1988 and 1991 ) .