I know what you mean, and it boiled down to simplifying how we analyze the data later. Non-mandatory questions can be skipped and it's tabulated as a skip or "none" on our side. We did it that way to try to speed up the time it took so people didn't need to go find "none" or 0.

We need much more data - especially from American Airlines and United flyers. From what we have so far, it looks like more people are flying Aegean Airlines than any airline which I know can't be the case.

I'm not allowed to cross post per se, so if you can nudge some of your friends toward the survey that would be fantastic. The goal is about 2000 respondents.