OK, OK, I understand. You (collectively) are neither going to give me the answer nor tell me, in simple terms, what more information I have to provide. I chose your group as being, in so far as I can judge these things, as the best around but as they say, 'the best is the enemy of the good'.
Come off it, Vando, just give us the actual 'presumptive probability'. You know, "Given the numbers you have supplied I would expect approximately x number of ships to have been both hijacked and sunk."
Sorry, I am used to people who conceptualise these not-exactly-knowable things by other means. However the following would be reasonable figures for ships, during their lifetime:
Probability of hijacking: one in a thousand
Probability of sinking: one in a hundred
Since I can't even follow the logic of your request, Stephen, and nobody else has responded, I will go elsewhere. Sorry to have trespassed on your time.
I belong to a group of people who, inter alia, (try to) apply Bayesian Theory to miscarriages of justice eg the recent spate of medical staff arrested when rare (but to be expected eventually) clusters of deaths occur in hospitals. A somewhat opposite case has recently arisen which has generated...