when chips are bagged they fill the bag half way then fill the rest with air then sealed.. this really didnt hit me until i opened the bag tonight when i realized it said “20% more chips”, but the bag was only halfway full if it were 20% more wouldnt it be filled more than halfway? where the heck is my 20% more chips!?
Biebs' World 
Ha ha. Yep. It does seem like a rip off. But you know, I think a lot of it has to do with the nature of the potato chip itself. Crispy and crunchy goodness.
When they fill the bag at the factory on the line, most of the chips are probably intacted. By the time the chips are boxed, put on a couple trucks, then shoved on the shelf, a good number of the chips are probably broken now. This along with the regular jostling in transit probably caused the chips to settle considerably.
Also if you try to squeeze an unopened chip bag, as you pointed out, there’s a lot of excess air. This is to keep you (or a pubescent grocery stocker) from crushing the everloving crap out of the entire bag of chips before you even get them home.
But don’t worry, the chips are sold by weight, not by volume. If you want more chips, you’ll have to buy the trash bag size that’s only half full. ;)
Lol, yeah I know what you mean. So buy 2 bags instead of one, I would.
Maybe they weren’t referring to the chips when they made the claim of “20% More!” It could have been the air, or the package, or the price…