I’ve been asked what will be the effect on the market of the iPhone 4S. Actually the question was what would be the effect on the market of there being no iPhone 5.

I’d answer that the iPhone 4S is a product designed to compete for two markets: (1) half the current iPhone users who bought a phone prior to the iPhone 4 and (2) non-iPhone users, typically non-smartphone users.

I’ll describe each market briefly.

The current iPhone users

Tim Cook said that half of all iPhones sold to date have been iPhone 4’s. That means that about 70 million iPhone 4’s have been sold. Those are not a target market because of three reasons:

1. The vast majority of those users are still paying for their iPhone 4 through the subsidy model used to sell them and to change phones today would incur a cash penalty.
2. Customer satisfaction surveys show that they have 90%+ satisfaction rating for their iPhone 4 and we can therefore assume that they are not looking for something better
3. Their iPhones are practically new and they still work and are upgradeable.

The other 70 million or so iPhone users have either a 3GS or a 3G iPhone. These are a very different market for three reasons:

1. They have already paid off their iPhones. They would not face any extra costs in switching to a new iPhone
2. Earlier customer satisfaction surveys showed that they once had 90%+ satisfaction with their product so they are likely to stay with the brand.
3. Their iPhones are getting old and beaten up after two years of use.

The current non-iPhone non-smartphone users

This market is so vast that it’s practically infinite. Over 1.5 billion phones are sold each year and Apple only has about 5% share. Therefore there is a vast pool of users who probably have been interested in getting an iPhone. These potential buyers will find the iPhone 4S an attractive alternative to buying a non-smart phone. They will also notice that there is now a range of price points for various iPhone models starting as low as zero.

Current non-iPhone smartphone users

I’ll add this market to complete the picture. This market is similar to the current iPhone 4 market because, except for Blackberry, most smartphones have been purchased in the last 12 months. This is especially true for Android phones. These owners of smartphones are unlikely to be interested in switching a phone that is “brand new” unless they have a very poor satisfaction with it. If they are not satisfied, there are many options, and iPhone is one of them. There are too many conditionals in this market and I therefore don’t think it’s a good target for the iPhone 4S.

So What are the prospects for the iPhone 4S (and other iPhones)?

The market for the new iPhones could then be summarized as follows: 70 million early generation iPhone users who are eager to upgrade (with 90% probability) plus a subset of a billion buyers of new phones next year who are looking for their first smartphone. These two markets iPhone 4S is targeting are “easy” because the competition is weak. It’s either “don’t upgrade my old iPhone” or “buy a dumb phone or another smartphone for almost the same price as an iPhone”.

I don’t see the result for units sold being different if there was a hypothetical iPhone 5 vs. the current iPhone 4S (and 4 and 3GS as a portfolio). In fact, a “better” iPhone would not be better at winning this competitive battle because the bar is so low.

So to answer the question in the headline: because an iPhone 5 is not needed meaning that it would over-serve the market and price itself out of contention.

The question will be very different a year from now when most early Android buyers will be looking for a new phone and when most iPhone 4 users (all 70 million of them) will be looking for a new iPhone. That would seem like a good time to introduce a new iPhone “5”.