http://news.teamxbox.com/xbox/15391/Latest-Xbox-360-Halo-3-Sales-Figures-Are-Astounding/

According to Microsoft, shipments/retailer sellthrough of Halo 3, Mass Effect and the Xbox360 console are:

8.1 Million
1.6 Million
17.7 Million

Remembering that there are going to be a larger percentage of units of software "in the channel" than there would be hardware, this means that Ioi is likely to be very close in his calculations. Here is what the totals would look like if we assume 25% of all software for new games is in channel, while 10% of all hardware is in channel (the estimate for hardware is lower because the system has been around for 2+ years, while the games are both less than 3 months old). 

Halo 3:  8.0 million
Mass Effect: 1.41 million
Xbox 360: 17.6 million

Ioi is still probably slightly undertracking Mass Effect, but it doesn't look like the estimations are egregious anymore. Both Halo and the 360 are nearly spot on, I suspect. Kudos!  

Do you really think there's 1.7 million xbox 360's in stores when the difference has usually been about 1 million between retail and sold through the other times? They didn't even stuff the channels this year and a lot of stores hardly had any of their systems a lot of times during the holiday rush.

wow, this site is quite accurate. Nice work ioi

yea i gotta agree with erikers that 1.7 million is quite a huge load to be in the channel unless they are stuffing. When they stuffed the channel they were around 2 million, but this time there were actually shortages in some places.