The fact that is would be an incredibly stupid thing to do? Kidnapping English citizens was a capital offense and piracy doubly so. If they started doing this routinely, they would have been hunted down by the Royal Navy.
I doubt many merchant captains had the forces necessary to kidnap large numbers of people anyway. Besides, It would have been much faster and more profitable to just go straight to Van Diemen's Land and drop off the 'cargo.'
To take my sophistry to its logical conclusion (at least I am admitting it :-) wouldn't this be only an specific solution for the Australia instance? can we apply this "rule" to the transport of, say, refugees?
All I am saying is, counting the cargo is not the most ideal solution for the Murdering Captain problem.
Sometimes you might even get willing participants. Say, a ship paid to transport 100 Cubans to the U.S for political asylum might just be better off bringing 100, paying Costa Ricans (ignoring linguistic identification :-)
I have an academic interest in this because I have been a refugee escaping on a boat, helped by traffickers to leave Somalia. And also, because I have an interest in the accurate identification of undocumented individuals (with their active participation, of course; adversarial identification is something better left to Langley)
Oh, it's a unique fascinating personal tale that I just happen to share with another 4 million people :-)
Survival stories are not worth telling if they're widely shared and experienced. In fact, there are people in New Orleans who have had it worse than us. Because of that, I prefer to be silent, and grateful.
I doubt many merchant captains had the forces necessary to kidnap large numbers of people anyway. Besides, It would have been much faster and more profitable to just go straight to Van Diemen's Land and drop off the 'cargo.'