It all depends on your angle, of course. Depending upon whether you sell music, make flash memory, run an operator, build devices, provide network backhaul capacity, design headphones, or a hundred other roles, your view of "what stat is important" will vary.
- Number of "music-capable" devices sold? (and do you include FM radio as well as MP3?)
- Number of "music-optimised" devices sold (eg a SonyEricsson Walkman phone vs a SonyEricsson Cybershot imaging-oriented phone which also has an MP3 function)
- Number of music-capable devices in use (ie addressable "installed base")
- Number of music tracks sold, intended for a specific device? Their value?
- Total hours of music listened to per user per day/week/year?
- Total # of people who have ever used their device for music, even if only once?
- Proportion of people who listen to music "regularly" on a platform
- Source of music listened to (or bought) - mobile download, sideload from a PC, split between online purchases vs CD rips vs peer-to-peer filesharing?
- Number of music devices per person and when/how they're used?
- Proportion of someone's total music listening given per "context" - mobile / car / home hifi / gig / club / friend's house etc?
- Total aggregate share of someone's entire disposal music-related expenditure?
- etc. x 100
Now, I've been engaged as part of a vigorous debate with the esteemed Tomi Ahonen, who stirred up a firestorm a week or so back with a hard-hitting piece on whether we should claim "iPod RIP". I'm not going to re-hash all the arguments, counter-arguments, flames and other stuff. It's all still burning on Tomi's site with small secondary conflagrations on places like the excellent Forum Oxford.
I'm certainly not going to get embroiled in the 14% / 76% market share debate. As the above indicates, there are at least 10 differently-defined "market shares" here, which are of differing importance to different people.
I have, however, tried to do an apples-to-apples comparison with some publicly-available data, which suggests that there may still a range of 2 orders of magnitude (ie a factor of 100) in terms of regularity of purchase of "music for devices".
Firstly - the UK. A market with a fairly good number of musicphones (however defined) and fairly decent 3G penetration, as well as high levels of music-fandom overall. In March 2006, the UK division of Hutchison's 3 mobile operator reported "With average sales of over 200,000 tracks per month, mobile media company 3 today announced that its audio service has made up over 53% of mobile audio track downloads since the start of 2006". In other words, in Q1 2006, the run rate for the market as a whole was about 400k songs to mobiles in the UK.
In Q1, 3 had about 3.5 million 3G subscribers, so it was selling 0.057 songs per sub per month = 0.69 songs / sub / year annualised. As 3 is the leader, this is probably a better rate of sale than the other 3G operators in the UK, ie probably an average 0.5 songs / sub / yr for 3G in the UK (particularly as other operators have more datacards subs). Another source has suggested "11% of 2G/2.5G users in Britain, and 32% of 3G uses in Britain downloaded music to phones" that suggests 2.5G users would perhaps be around 0.15-0.2 songs / sub / yr , and probably (average across all UK subs, probably around 80%+ 2G) about 0.25 / sub / yr averaged across the whole UK mobile population.
Japan is one of the most advanced mobile music markets. KDDI has now downloaded 50m songs, with the last 20m sold between Dec '05 and May '06. ie a run-rate of 4m / month and thus 48m / year. It has 24m subs, so this is 2 tracks / sub / yr. I've seen something else (can't find the source unfortunately) which suggests that 23% of its users download music, so this average figure is skewed between lots of people on zero, and a smaller number on much higher figures.
Conversely, Apple has around 40m iPod users as an "installed base" of users. It had sold 500m iTunes songs in July 2005 and 1bn by Feb 2006 ie a run-rate of 71m per month, ie 1.8 / owner / month or 21 / owner / year.
All this obviously excludes music ripped from CD (or downloaded from other legal/illegal Internet sources) and put onto iPod or phone by USB or memory card. However, to sum up - legal device-oriented full-track music sales, averaged across all users/subscribers (yeah, I know definitions are a little different & some people have several phones or iPods) are:
UK mobile - about 0.25 songs / sub / year, rising to 0.5+ among 3G users (and using some other stats I've seen on what % ever download any music, probably about 2 songs / active mobile-music sub / year)
Japan mobile - about 2 songs / sub / year (and at 23% of KDDI users downloading music at all, about 11 songs / active mobile music sub / year)
iPod - about 20 songs / user / year
I reckon that's about as close to "apple-to-apples" as I can get on published data.
Disclosure: I own an iPod Nano, 3 different MP3 playing-phones and never buy songs from iTunes or via operator download, preferring to buy & rip CDs instead & use USB and memory cards.