The other day I was trying to think of information leaks that a competent conspiracy couldn’t prevent, regarding this. I just thought of one small one: people will sometimes randomly die or have their homes raided. If the slavery is common, then sometimes the slaves will be discovered during these events. Even if the escapees wanted to silence the story out of shame, cops would probably gossip to the press.
So you can probably tally such events, crunch the numbers, and get a decent conspiracy-resistant estimate.
The other day I was trying to think of information leaks that a competent conspiracy couldn’t prevent, regarding this. I just thought of one small one: people will sometimes randomly die or have their homes raided. If the slavery is common, then sometimes the slaves will be discovered during these events. Even if the escapees wanted to silence the story out of shame, cops would probably gossip to the press.
So you can probably tally such events, crunch the numbers, and get a decent conspiracy-resistant estimate.