Are employees required to disclose purchases and sales of their own companies stocks? If yes, are these disclosures publicly available? If yes, where?
Where do companies such as INK Research get their "insider" data?
Have a look at Decoding Inside Information. From Section II (Data):
The whole paper is very interesing. From the intro:
Form 3 and Form 4 are used for this. When you look at a company's SEC filings, you may see these. They are used when large shareholders make moves, as well as insiders (who will generally always be large shareholders)
SEC's edgar online database will have these filings available for the public.