>>5782852Shounen Jump compares manga to OTHER manga, so you know how popular that one is, and use fan letters/Internet comments/reviews as a thermometer about the story, there isn't much polling viewers about the series specifically.
They do have a character popularity contest and sometimes the story takes a turn based on who's more popular.
However, most of the creative decisions/changes/solutions come from the editor's intuition from his experience in the market, all the rest is just raw data and doing what the public wants is not necessarily the best way to go about things.
