You should put "Christians" in quotes for that sentence.

If you're talking about full on church-going, follow the bible on all 7 days of the week, and believe every word in it as a Christian is supposed to, then no way are they in the majority.

But you could ask a million people individually "Are you a Christian" and the HUGE majority would say yes, even though they are not practising, don't "really" believe in it, it's just that they were brought up in a Christian-ish household. But they still answer "yes" to this question.

Then there are all the ones who just pick and choose what they want from the bible yet still call themselves Christian, even though they have technically started a new religion. It's these ones that are in the majority today.