But for a more sophisticated attack, like the one you describe, we do have a lot of defenses in place. So just to name a few, we do things like requiring a verified phone number from a trusted carrier, just to increase the probability that we're dealing with real humans. We look for raters who have rated things very similarly in the past. And actually, we might treat them as the same person just to limit the influence of really similar behavior. Another thing is we can look at random samples of raters, and if they're rating things very differently than self-selected, possibly malicious raters, then that's a very important signal. And we have other things too: there’s “rater reputation” to deal with low-quality people.