AdMob has announced that it has served its 20 billionth mobile advertisement. In the last 12 months, the company’s impressions have grown from 500 million a month to 2.5 billion per month today.

The 20 billionth impression was from financial services conglomerate HDFC and was served in India at 1.56 GMT on Tuesday March 25th. The user was browsing Cricinfo’s mobile site on a Nokia N70.

A couple of other interesting points:

• Reach is starting to grow - AdMob can reach 40% of US subscribers with a mobile internet capable phone. (36 million subs)
• The AdMob fill rate is around 95%.
• Over 3,900 mobile websites us the AdMob platform - I’m not sure I knew that 3,900 mobile sites even existed!

“This is an exciting milestone, but we’re most encouraged by the progress we’ve made on the underlying platform and technology that powers our marketplace. Our relevance and optimization efforts led by our team of statisticians and researchers have already yielded double digit gains in our ability to monetize our publisher’s sites. I’m very confident that over the next two quarters we will be making significant product enhancements and releasing entirely new solutions that will further unlock the true potential in mobile.” said Omar Hamoui, AdMob’s founder and CEO.

(see the MobiAD interview with Omar: “Outpacing the Competition“.)

“The AdMob network has demonstrated consistent, significant reach, and has proven to be a valuable customer acquisition method for EA Mobile (Electronic Arts),” said Adam Sussman, VP of New Business Development.

See the full release here.