What materials produce higher levels of static electricity?

[Thies_Kohl]

A lot of people know the example of a carpet and a doorknob. You accidentally rub your foot to the carpet and then get a static shock after touching the doorknob. Why does carpet produce higher static electricity than for example hardwood or something. Is it because of the hairs? Is it because the surface is bigger?

 

[anuttarasammyak]

In general answer, it is insulator. You may search "insulator" to find what kind of materials have the largest insulation.