Last year, every consumer brand seemed to be building an iPhone application. Towards the end of 2009, they began to say, 'We have an iPhone application. Now what?" For many, the answer seems to be "mobile Web." The open question is "how." I'll be publishing an in-depth study on how with my colleague Brian Walker, going into more depth on the implications of commerce for mobile Web builds. One of the strategic questions that must be answered first is, "do I build a mobile Web site for all devices (= long tail)?" or "do I have a more tiered approach with custom development for the handful of devices (short tail) which drive most of my traffic and a more automated approach for all the other devices (long tail)?" Good questions.

There are some good sources of information online. AdMob and Millennial Media publish monthly reports based on ad requests they see. Netbiscuits just published a white paper with a lot of good data.

First, how long is the long tail? According to the Netbiscuits white paper, it was 2,496 devices in February 2010. How short is the short tail (= 50% of the traffic)? In February 2010, only 12 devices. What is the number one device in each report? Yes, the iPhone — or now iOS 4 platform. In terms of global traffic, Netbiscuits put Apple first with 36% of traffic while AdMob's numbers for Apple were a bit lower at 33%.

How long the long tail is and how short the short tail is varies by country. Netbiscuits provides some interesting insights taken from the page requests for a mobile site monitored in four different countries. The short tail in the US? 2. Yes, 2. The long tail — 1,687. Wow. Who makes those 2 devices? Apple. And Apple. The short tail is longer in other countries. In the UK, it is 9 devices according to Netbiscuits. In Germany, it is 2, but Nokia claims the second spot. In Australia, it is 4. While Apple has more than 50% of traffic in the US according to Netbiscuits, it "only" has about a third in the UK and Germany.

Is the short tail getting shorter? In some countries, yes. Between May 2009 and February 2010, the short tail in Germany decreased from 9 devices to 7. Still it is important to notice that short and long tail vary not only by country or time, but also by the kind of content or service offered on the mobile Web.

Of course, the US and Western European markets are very different than those in Asia and other parts of the world. Malaysia, the Philippines, and Indonesia have different short tail and long tail profiles. First, the short tails are much longer. In Indonesia (according to AdMob data), the top 3 devices are only about 10% of all of their traffic — or ad requests. In the Philippines, the top 10 devices only deliver 30.6% of ad requests, with the iPhone and iPod touch delivering only about 7% of traffic. Apple isn't even the number one smartphone here. In Malaysia, the short tail is 26 devices. These countries are much more fragmented.

So what about this short tail of Apple and Android here in the US? You should check out AdMob's April report. They do an extensive breakout of the two platforms as measured by ad requests — their proxy for traffic. The iPhone is mostly about a NA play, but only 49% of unique devices are in NA. Another 28% are in Western Europe. Android? AdMob shows 75% of devices in North America. AdMob still sees a 2:1 ratio of iPhone OS devices to Android OS devices. Other notable trends in the AdMob report? While Apple still leads in traffic, their percentage of overall traffic (ad requests) has been dropping this year — from 51% of smartphone share in January 2010 to 42% in April 2010. Android has grown some — from 21% to 25% in the same period. Who is gaining share? Nokia — growing from 19% to 23% in the same period.

How long is your short tail? Depends. For at least one of my clients, the top two devices are 90% of their mobile Web traffic. This puts their short tail number at 1. Their number two device falls into the long tail. They have 1,500+ devices combining for less than 10% of traffic. Not every situation is this extreme. As you are planning your mobile Web implementation strategy, it is worth analyzing. You want to make an explicit decision on how you want to cover the full range of devices, even if this means a tiered approach.

Millennial Media published less traffic research in their latest report. They focused more on the effectiveness of campaigns. Worth a read.