Quote From Thesisfun:
a- Fine- just acknowledge previous papers (also bumps up your H-index :) )

b- Presumably methods are different somewhere or are you just splitting up to get multiple publications (that is bad form).

c- What Rewt suggests is just wrong!!! There are fields where authorship has very specific requirements (including approval of the final paper). Why is supervisor not available?? Depending on what future relationship you want to have, you could send the paper to supervisor with a reasonable deadline saying that you plan to submit by a certain date and would like comments/ approval by then or will be unable to include as author!

Quote From rewt:
Never worked with demographical data or that field but I would initially publish one paper in a high impact journal. Once it is accepted/published you can reference that methodological and that data set (boost your citation score). The other two papers will cite the original and there will be no plagiarism issues. I don't think submitting three papers simultaneously together is a good idea, but I could be wrong.

Unless he owns the data you can publish without him. Though he did contribute to the work by supervising you, so you should add him as an author. This is a grey area but unless he specifically doesn't approve, I would add his name regardless of him reviewing the paper.