Here's why:

* Structure: Paper is made primarily of cellulose fibers, which are long chains of sugar molecules. These molecules are held together by strong covalent bonds, which don't easily allow for the free movement of electrons.

* Electron Mobility: Insulators have tightly bound electrons that don't readily move from atom to atom. This makes it difficult for electricity to flow through them.

* Resistance: Paper has a high electrical resistance, meaning it opposes the flow of electricity.

However, there are some nuances to consider:

* Moisture: Paper can become more conductive when it's wet. Water molecules can carry charge, and if paper absorbs enough water, it can become a better conductor.

* Type of paper: Some specialty papers, like those treated with conductive materials, might be more conductive than regular paper.

In general, you can safely assume that paper is a good insulator.