I can see where some people may prefer the 4" size, but I just don't believe it is really 60% of people. I think they need to quit using the how many iPhones are being used metric, and instead get a poll of current iPhone users to see what their preferred size is.
Oh yea, of course it isn't 60% of the total, but I think it's more than many believe. *IF* Apple actually makes a 4" iPhone with similar enough specs to the 6s, I'd bet it would sell 60%+ as many as the 6s. So, I'd guess that if everyone were starting over and buying a new iPhone today, it would break down something like 4" = 30-40%, 4.7" 50-60%, 5.5" = 10%.
BTW, MacNN did a poll of 1000 Apple-store patrons outside of an Apple store on the east coast last month, and about 8.9% preferred a 4" size. But, the problem, IMO, with such a poll is that a lot of people just have spec-itis, in that they believe bigger is better, just because, until they've actually spent some time considering the pros and cons.
This is crazy. Before the iPhone 6 and 6 plus, they were reporting everyone was dying to have a larger iPhone , now that we have larger iPhones, now they are saying people want the smaller iPhone !! Which one is it ?
It is both! For people who prefer screen-real-estate over the implications of size (yes, there are actual downsides), they wanted a bigger phone, and are quite happy with the 4.7" and 5.5" models. For people who care about a more optimum size in the hand/pocket, and often use their phone in addition to a computer or tablet, the 4" size is preferred.
Unfortunately, Apple didn't really give us a choice. They just moved to bigger models and left people wanting a smaller device to increasingly outdated equipment.
BTW, I think this latter trend is a big mistake, aside from a post-new-model-launch fire-sale to clear the channels. For a company like Apple that is *supposed* to be focused on user-experience, and is moving quickly with the technology and software upgrades, it's a bad idea to be selling outdated models as new.
If they really need to have a budget model, make it current tech with feature limitations. But, the CPU/GPU/RAM need to be pretty consistent across the line. I wouldn't buy ANY new iOS device today without 2 GB RAM. (And, there seems to be mixed signals on this, as Cook is saying they don't need budget models, while their model lineup is full of old models at semi-budget prices. That said, I'm not even sure Apple knows what they are doing anymore!)