HIP isn't used for harvest estimates or to set bag limits. It's mainly used to select who will fill out the more in depth season long hunt log. I did it back in 2008, and had to record every hunt, hunt location, duration, and species harvested (duck, goose, etc).
http://www.fws.gov/hip/"In addition, when you sign up for HIP, you will be asked to voluntarily answer several questions about your hunting experience during last year's season. Y
our answers to these questions are not used to compile harvest estimates, but are simply used to identify what types of birds you usually hunt. This allows the Service to mail its surveys to the appropriate hunters. For example,
most surveys about dove harvest are sent to hunters who usually hunt doves, while
most waterfowl harvest surveys are sent to hunters who usually hunt ducks and/or geese."