Since the start of October two interesting but otherwise unrelated pieces of research have been published. Read in combination, they help explain why The Guardian is to introduce a paid app for the iPhone but not, as yet, for any other platform.

Leave aside for the moment the fact that both the iPhone and the iPod Touch share the same screen size, the same operating system and come from the same manufacturer.

Thanks to their uniformity, app writers face far less of a challenge than they do when attempting to develop for both resistive and capacitive touchscreens of varying shapes and sizes, along with possibly differing ‘flavours’ of the same operating system.

But that is not the reason why apps for Symbian, RIM, Windows Mobile and Android OS will remain unavailable, at least for the moment.

Instead the rationale is far simpler. For explanation simply look at the AdMob Mobile Metrics Report for August. There, it is revealed, the Apple operating system accounted for no less than 66% of all smartphone traffic.

By comparison, the share of phones using the Symbian OS was 17%, Android 10%, RIM (BlackBerries) 6%, and Windows Mobile a measly 1%.

With impeccable logic, even if that might run counter to what is often argued editorially, The Guardian have merely acknowledged the inescapable inevitability – the market will decide.

Few will disagree that it clearly makes sense to focus development on a single app capable of satisfying two thirds of all users, rather than dissipating your efforts attempting to cater for a multitude of minority audiences.

Since February, the Apple share has grown from 57% of all smartphone traffic, while that of Symbian has declined from 35% and Windows from 3%.

Conversely, both RIM and Android have also increased share, from 4% and 1% respectively. Even so, those shares remain comparatively small and, despite Android’s impressive growth, unlike the Apple customer base, Android users remain disinclined to pay for apps.

However the AdMob numbers are not definitive. They only represent those mobile devices to which AdMob have served advertisements during the month.

That said, in the UK alone during August AdMob served no fewer than 428.2 million ads, 35.5% of which were to smartphones. As a result their findings should be reasonably indicative of those smartphone users visiting media sites. And those are the users of interest to The Guardian.

The other piece of research was undertaken by The Association of Online Publishers, whose members include The Guardian, along with Murdoch’s News International, The Telegraph, the Mail, the Independent and The Mirror.

No fewer than 83% of AOP members thought “the iPhone has transformed the opportunity for mobile internet.”

And, in answer to the question, “what distribution channel will become more important in the next 12 months?” 69% of AOP members who responded said “Mobile”, and 67% “Mobile Apps”.

As a result mobile internet development was thought to be the biggest trend expected in the next 12 months, with 86% of respondents either already providing or intending to provide mobile sites, or optimise existing mobile sites.

More pertinently no fewer than 56% of respondents expected to develop ‘paid for’ downloadable apps.

In other words where The Guardian is leading, others intend to follow.

If you want to be able to read news optimised for your mobile the odds are you will soon have to pay. If you want it for free, or you don’t own an iPhone, you will be forced to forgo the bespoke app and instead continue to make do with the existing all-purpose website.

In the immediate future it seems the choice will be yours. And if you only have to make a one-off payment of less than a fiver, you might be happy to pay for apps enabling you to read a multiplicity of papers.

However, it’s unlikely that media owners will be satisfied with a single small payment for very long. So, having got you to accept that news is worth paying for, anticipate the introduction of weekly, monthly or annual subscriptions.

That though may not happen until the arrival of the iTablet and other such similar more reader-friendly devices.

The pros and cons of paid-for content have been discussed here and here previously.

Now it is no longer a question of if or even when. Only of how soon and how much.

And crucially, at least where media owners are concerned, how many of us will pay.