From Longman Dictionary of Contemporary Englishyour guess is as good as mineyour guess is as good as minespokenDON'T CARE used to tell someone that you do not know any more than they do about something → guess
Examples from the Corpus
your guess is as good as mine• "When's the next bus coming?" "Your guess is as good as mine."• "Who do you think will win the World Cup?" "Your guess is as good as mine." 