Matthew 7:22-23 “Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? And in thy name have cast out devils? And in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.”
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Matthew 7:13-14 “Enter ye in at the strait gate: for wide is the gate, and broad is the way, that leadeth to destruction, and many there be which go in thereat. Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it.”
We know from the words of Jesus that "few" find salvation. Few is less than 50% by definition, and the actual percentage of those saved is most likely much, much, much less than that.
In America, supposedly the most Christian nation on earth, I would estimate that the percentage of those who actually are saved by faith in Jesus Christ to be in the single digits. It could be in the low teens, but I doubt it.