IME, I'd place it at 1-2 out of 10, conservatively.
One needs to remember that they are farm made and raised and that we, in the "ornamental fish trade", get a tiny fraction of what goes to food markets and we get more runts and genetic hick-ups and culls as the farmers view them as having smaller chances of reaching marketable size in the right time. Hence, instead of tossing them, the farmers get a little bit of return on the "unlucky" ones yet.
A small fraction of them appears to be w/c but IDK how many of those claims can be trusted. Why spend all this energy to get them out of a river when you can walk up to a vat of a myriad of them and scoop up a few hundred in one net sweep? The overhead may be incomparable. But licensing should be factored in too... So, sure w/c happen, but I tend to think it is a far smaller percentage of them than we are made to believe.