To answer this question we have to look at both subjects seperately. We have to ask ourselves what exactly is a Demon? Most people would answer this as being one of Satan's helpers. Hell's version of Angels if you will. This makes them a very specific subset of being. As with any being their powers are limited and have a specific scope although from a human point of view those powers may seem limitless.

Just as the Angels have their jobs, the various demons have theirs. Their powers will be suited towards the performance of those jobs and their activity will be focused on accomplishing that. The thing to remember though is that a demon has the need to be exceptionally subtle. They don't corrupt through force, it wouldn't make sense for them to corrupt through force. Just as Satan is the father of lies his demons use this same trick. They may first appear as beautiful, kind, and caring but just long enough to get you on their side, then the true face is revealed but you will probably be too far under their control to worried about it.

The specific point to remember is that demons deal with humans. Some of your so-called "Demonologists" will place them in long abandoned houses, prisons, and mental hospitals. What sense does it make for a being that is focused on corrupting human souls to inhabit an empty building?

Now most of this has been dealing with the Christian version of demons.  The truth is every culture in the world has a version of what we would call demons.  The common thread between all of them is that these beings are evil with a capital E and they prey on humans. 

Now when dealing with Paranormal Activity you first have to understand what exactly Paranormal is.  Put simply the word Paranormal is a very generic description for any activity that is outside the range of current scientific understanding i.e. Ghosts, Ufo's, Aliens, Bigfoot, El Chupacabra, Shadow People, and of course Angels and Demons.

So while demonic activity can be classified under paranormal, not all paranormal activity involves demons.  Now there are no real statistics to be able to use when explaining this but then I've never liked statistics much anyway.  The simple fact is that Demons are just one small subset of the entire paranormal realm and make up an amount of activity in proportion to that subset.

Now some Paranormal Investigators and most of the dime store "Demonologists" out there will have you believe that all Paranormal Activity involves the demonic.  This is a narrow minded, and quite bluntly idiotic view point.  When you begin to believe that anything outside the range of our understanding is demonic you start painting with a very wide brush, this would also mean that the same powers they supposedly use to get rid of demons is in itself demonic.

Now rarely will an investigator run into true demonic activity, even more rarely will an investigator recognize it for what it is.  Most will resemble a basic haunting, some will be more extreme and may or may not be darker in nature.  They will however have more power than a regular haunting and of course will be more dangerous than a normal haunting.

In summary, while all demonic activity is paranormal not all paranormal activity is demonic.

Thank you for this question.

Dustyn