Regarding calls, do you have suggestions on how to figure out if the OI in some particular call is mostly market makers' short or investors' short?

I know you referenced "good feel for the underlying and market participants" in order to answer that question, but I'm wondering if there's a specific idea you could suggest regarding that to help narrow my focus?

> It is not just market makers that sell calls

Would you guess that market makers are, on average, net flat, net short, or net long calls?