Shrinkflation
So, I found out a fun fact this last weekend!
Every state has a Department of Weights and Measures. One of their jobs is to make sure that companies are actually selling you the quantities they claim they're selling. For example, this is the department which tests gas pumps and makes sure they're really pumping out a gallon of gas when they charge you for a gallon of gas.
If you happen to, just as an example, notice that your 1lb (16 ounce) box of San Giorgio spaghetti actually only has 10oz of noodles, and you weigh your other boxes of spaghetti to discover they run from 10 to 14 ounces but never the full pound they're supposed to have, and that's why you never seem to have enough pasta for leftovers the next day, then you can report that to the Department of Weights and Measures.
They will want to know where you bought the item, and then will investigate whether the store or the manufacturer is routinely shorting customers. If they do, they will issue a fine to the offending party, you will be eligible for a refund, and under some circumstances lawsuits may follow.
Now, I don't know the outcome of the complaint I just initiated, but they did not want to know specific receipts or times of purchase. Which is good for me as I didn't keep any of those things, at the time I just said "Wow, fuck San Giorgio" and switched brands. But this is still enough to get an inspector out.