A silly question. But if you want statistics, I would say that 90% of those who celebrate Halloween are being deceived by a system instituted by Satan. But maybe 10% are actively worshipping Satan and doing darker deeds than trick or treating on Halloween. But both ways Satan's purpose is served. As the article says:
Frankly, Halloween is anything but harmless. It focuses one's attention on witchcraft and demonism, which flies in the face of the holy God Almighty! When parents not only allow but also encourage their children to celebrate witches and goblins, they are teaching them that it's acceptable to deal in demonism.
And we have seen what God thinks of that. God is a God of light and truth (1 John 1:5). Satan, "the god of this age" (2 Corinthians 4:4), is a very real being—a being of darkness, deception and death (Revelation 12:9; John 8:44). We are to have nothing to do with his ways. (To learn more, request our free booklet Is There Really a Devil?)
Do not assume that Halloween is a harmless holiday. God hates mankind's dabbling in the spirit world of Satan and his demons!
If there were no other reason available, that should be enough. But there are more reasons. Halloween keeps humankind, and many Christians, confused, disoriented and separated from the one and only true God.
God is not the author of confusion (1 Corinthians 14:33). Nor is He the author of Halloween or any other "Christianized" pagan holidays (Amos 5:21). Why would the only true God who loves mankind support any worldly holiday that blinds human beings to Him and His truth and that holds men, women and children captive to deception?
"I would say that 90% of those who celebrate Halloween are being deceived by a system instituted by Satan. But maybe 10% are actively worshipping Satan and doing darker deeds than trick or treating on Halloween."
You must live in a tougher neighborhood than I do. Here in suburban Northern Virginia, it's all about the candy.
I wouldn't even say 10 percent of Satanist are actually worshipping satan.