[snake42]

In the article it says:

To account for possible changes in package sizes, we focused on the price per unit, whether it was an ounce of salsa or a square foot of aluminum foil.

[LeifCarrotson]

It doesn't say that they accounted for possible changes in item quality. Tide detergent claims that their new 80-oz bottle of laundry detergent can wash 64 loads just like the previous 100-oz bottle because it's more concentrated, and I suppose NPR (if they'd retained a sample of the previous product) could have brought that to a chemistry lab to test and verify that claim, but I have no idea how you'd objectively prove that an ounce of salsa had truly remained the same product.

[snake42]

Sure, but they are accounting for size shrinkage which the original poster was saying they didn't.

I don't really know how you can account for quality either. User surveys? Ingredient sourcing? But then again I think this kind of reporting is just a general barometer. Some other comments are pointing to data sources that might do more of this.

[queuebert]

Laundry detergent is usually priced as cents per load by savvy shoppers. That would factor out smaller doses.

[Aloha]

At some point it will be concentrated it'll be powder again ;-)