This entire discussion depends on how we're defining "churner" or "churning." Does apping for 1 card bonus and then closing count? When I think churner, I think of someone addicted to myFICO with 20-30 inquiries on a single CRA, probably a heavy traveler. Clearly there are not 5 million of those in this country.
The 1.5% number comes from the assumption that there are 5 million churners on a CC product, causing the bonus to go away. If we're talking about ANYONE who has ever apped for a card only for the bonus, obviously the percentage is much larger and CCCs lose a lot of money. The assumption that there needs to be a huge chunk of hardcore churners for bonuses to be shut down is probably not accurate. I don't think it takes much for CCCs to start shutting down bonuses. By @mountaindewvoltage's approximations, it doesn't take too many career churners, one in a whilers, or even one-timers to gun down bonuses before the bank starts losing some major money. They're now starting to discover that people are still getting the cards without yummy bonuses. It need not take the proverbial village of high volume churners to bring down these bonuses, at least the super 40k+ ones.
