Tracking the state of the mobile ad market is tough when you’re owned by Google. That’s what AdMob decided today. The mobile ad network published its final Mobile Metrics Report today.

Google’s Android phone may be making inroads with consumers, but if Apple is going to prevent AdMob from selling targeted ads on its devices, it hardly seems necessary for the company to continue documenting Apple’s impressive sales figures. That said, it’s still interesting to see where the two companies are shaping up in the mobile market.

AdMob serves ads for more than 23,000 mobile sites and apps. But recently Apple announced only “independent” mobile ad networks could collect data
on Apple users and target advertising on its products
. Considering that AdMob was purchased by Google for $750 million, the company’s prospects on the device in the near future look rather bleak. 

Which also helps explain why AdMob might take a break from compiling this reports. Aside from the fact that AdMob is now firmly commited to Google’s ad business, creating analytic snapshots of your industry is only good if you can sell inventory across the gamut.

AdMob’s status in the mobile market explains why the company might not want to do the reports, but it also makes reading the numbers a little more interesting.

AdMob’s report shows that mobile traffic around the world has grown at least 4 times since May of 2008.But in this case, it also clearly lines up where Apple and Google are growing in mobile. Smartphones now comprise almost half of mobile ad impressions. Two
years ago they comprised 22% of total mobile ad impressions. Now
they’re up to 46 percent in May 2010. 90% of worldwide smartphone requests were generated by iOS, Android and Symbian.

24% of mobile traffic came over wifi in 2010. That’s set to explode as more people start using smartphones (and part of the reason that telecoms are no longer offering all you can eat data plans).

iPhone is going strong outside of America. The strongest growths in sales of the devices in 2010 came in Western Europe, Oceania and Asia. Meanwhile, Android is developing a base in Asia. China is the second largest market for Google’s smartphone with 13% of users. Of all Google handsets, the Android is the most popular, with 21% of users.

In a head to head comparison, iOS devices outpace Android devices two to one in America. Worldwide, the divide gets bigger, with 3.5 iOS devices to every Android phone.

Predictably, iOS also outperforms Android in the apps department. Twice as many iPhone users regularly download apps compared to Android users. Meanwhile, half of iPhone users download apps every month, compared to 21% of Android owners.

However, the amount spent on apps is pretty comparable. iPod touch users spend about $11.39 monthly on apps, versus the $8.18 spent on iPhones and $8.36 on Android phones.

iPhone users also have a slightly higher opinion of their phones. 91% would recommend their device to others, compared to 84% of Android owners.