Nahhh, this isn't the how-many-angels-fit-on-the-head-of-pin question.
This is a the-devil-made-me-do-it question. Demons get blamed for every sin we do. It seems to me that, if that is true, at least one demon must follow a person -- all people -- for there whole lives. And there are 7.6 billion people in the world today, with the population growing exponentially now, so I'm just covering how many demons will be needed before 2020.
As far as I know, (and we really don't have very much info on demons -- nor angels), demons don't grow up, get married, have babies and raise the babies to become productive demons, so do we really each have a demon following us around? How many are there to do that?
Or.... can we take on the responsibility that the-devil-did-not-make-me-do-that?
I figure there are many more than 8 bln.
The bible shows that new angels and demons are created all the time.
If you look at the Hebrew and Greek, you would see that at least certain kinds of demons and angels can and do multiply themselves.
Take a look at the spirit that was on Moses, how it went on the 70 elders.
You might say that it was the Holy Spirit that was on all of them, but if you look at the original language, you would see that God took "a part of" the spirit that was on Moses, and put it on the others.
And what about the devil, when he wanted to be like the most high God.
Again, if you look at the original words you would see that he spreads himself out, or multiplies himself.
Ever wonder why Jesus asked how satan could cast himself out when it was another spirit that he was casting out? For He said, "if I by Beelzebub cast out devils".
Jesus called both beelzebub and devils, satan.
Why did He do that?
And How can Abraham be our father and God be our Father at the same time?
Everything recreates itself, whether it be natural or spiritual.
Didn't God say His word was spirit.
There's a lot of God's word out there.