Xcode 4.3's 'estimated app store size' is considerably different than .ipa file, why?

Question

I had been using Xcode 4.2 up till last week and I was using the size of my .ipa file to estimate the size of my app in the app store (I\'ve kept it just under 20MB) and its

Answer 1

The App store encrypts most of your binary executable, which renders it no-longer compressible inside the new ipa file that the App store creates for each customer. You have to look at the uncompressed size of your binary executable and add most of that size to your zip-ed .ipa size to get the new App store .ipa size.