One needs to remember that Ferrania supplied most of the huge European and British photo labs with their "free film with D&P" offers for decades. It didn't have the Ferrania name on it, but it was made by them. Big supermarket chains applied their name to Ferrania film. Small chains of cameara shops too, all across Europe. And they did sell under their own name too.
But often the only clue was that "made in Italy" label. Ferrania made 35mm, 120, 127, 126 and in vast quantities...though it would be true to say that Kodak might have edged them out in terms of sheer numbers because the Ferrania film was squarely aimed at the amateur snapshot photographer. Which is not to say it was bad at all. But it wasn't Portra. It was definitely available in the USA too, though I am less familiar with that market at least prior to the mid 1990s. I do, however, recall buying Polaroid branded film at Wal-Mart circa 1997 which was absolutely manufactured by Ferrania. They made 8mm and super 8 cine film too.
I've still got a ton of negatives which would have been sold as "Prinz Color" (Dixons house brand name for photo gear) because I grew up near the vast Photo Trade Processing lab which handled Dixons and Photopost D&P. Just that lab alone must have shipped millions of films. It was truly huge. I had a tour of just part of it as a child and I'd never seen a building so big. And that was just one customer of Ferrania, in one country....they had the similar market throughout Europe.
Maybe Kodak was bigger. We'll never know for sure. But for sure, Ferrania were producing more camera film than the others Fuji, Agfa, Konica/Sakura, Ilford. It's just that most of it didn't carry the Ferrania name and logo.