Brands reformulate for good reasons: a cheaper supplier, a cleaner ingredient list, a regulation, a better product. From the repeat customer’s side, the product they chose has been replaced without their consent. The label says the same thing and the product doesn’t.

What happened in 1985

Coca-Cola’s lead over its chief rival had been slipping for 15 years when it decided to change the formula for the first time in 99 years. Nearly 200,000 consumers took part in its taste tests, and the new formula was preferred. The change was announced on April 23, 1985. Calls to the company’s consumer line went from about 400 a day to 1,500 a day by June. A customer named Gay Mullins started a group called Old Cola Drinkers of America. On July 11, 79 days after the launch, the company brought the original back as Coca-Cola Classic Reported.

Company president Donald Keough said all the consumer research “could not measure or reveal the depth and abiding emotional attachment” people felt to the original Reported. To those who suspected the whole thing was a stunt, he said: “The truth is we’re not that dumb and we’re not that smart” Reported. The new formula was renamed Coke II in 1990 and discontinued in 2002 Reported.

Sources: The Coca-Cola Company’s history of New Coke; CBS News, 2015; History.com. Call volumes differ between accounts; these are the company’s own.

What the research missed

The taste tests asked which of two sips people preferred. They didn’t ask how people would feel if the one they drank every day were taken away, which is the question the launch actually posed. The research did pick up a warning. Later histories of the company report that a minority of testers were angry at the thought of a change and said they might stop drinking Coke Reported. A minority of testers is easy to dismiss. It was also, very likely, the loyal core: the people most attached to the product and most likely to buy it every week.

A taste test asks which one people prefer. A reformulation asks whether they’ll accept losing the one they have.

So test a change on current heavy buyers, and ask “instead of,” not “compared with.” Treat the angry minority as the signal: they are the dependents from chapter 7. And write down, before launch, the reorder rate among existing buyers that would make you reverse. Coca-Cola reversed in 79 days under public pressure; you can decide in calm.

The reformulation playbook

1. Ask whether they’ll noticeA new supplier for an identical ingredient may be invisible. A new scent, texture, taste, fit, size or active ingredient won’t be. If they’ll notice, it’s the discontinuation playbook from chapter 8, with the replacement already chosen.
2. Tell them before it arrivesExisting buyers, and especially subscribers, hear about the change before the new version ships: what changed, why, and what they’ll notice. Discovering it in the product reads as something slipped past them.
3. Let them try it firstA sample of the new version in their last order of the old one. Ask what they think, and read the answers.
4. Offer the old one while it lastsSell remaining stock of the old version to the people who want it, as a last-chance stock-up, instead of blending it out quietly.
5. Watch the reorder rateExisting buyers’ reorder rate for 90 days, against their rate before the change and the rollback line.

For supplements, cosmetics and food, a formula change can also change what the label must say. Have counsel or a regulatory specialist review the new label and any “new” or “improved” claim.

Do this

• Ask operations for every change planned in the next six months to a supplier, formula, scent, fit or pack size on a reorder product. For each, decide whether customers will notice. Put the ones they will into the playbook now.