Here's a more detailed answer from our tech dept.
"While unusual, these are far from impossible. I went through the database just now. At the end of the day Friday, ATU had 4 puts, and 0 calls. The put / call ratio should be positive infinity. We use a number somewhere around 2 billion. If you ask for stocks with a put/call ratio of over 100, I specifically wanted stocks like this to appear. If you ask for stocks with a put/call ratio below 100, ATU would disappear.
MDP was a similar case, with 7 puts and no calls. As was BND with 4 puts and no calls. YTEC with 20 puts and no calls. Lots more exactly like this.
IBKR had a put call ratio of 139. That was 695 puts and 5 calls.
And, of course, there are similar results on the other side. AEE ended the day with 0 puts and 3 calls. So the put call volume would be 0.
What do all of these have in common? Relatively low volume. In fact, if you did this test shortly after the open, rather than late in the day, you'd see a lot more of this. You reduce this effect by setting a minimum put call volume. And you should also be careful using this filter in the early morning.
Also, remember that the oddsmaker will cut you off after a certain number of entries. If you have a query that matches a lot of stuff, and another one that matches twice as many things, they might both give you the same number of hits before they give up. If you want to see how many stocks matched, try using our history feature our our intraday top list.
To answer his specific question, it works as advertised for values between 0 and about 2 billion. If he put in 3 billion, that would break our assumption that 2 billion and positive infinity are approximately the same."
