It even has the added benefit of people eating less pre-packaged crap.
As others have said in this thread, if you want to be honest with costumers make supermarkets add price/100g next to the price label.
No. The issue is that consumers tend to remember the price they last paid for a product, but seldom remember the weight/volume of the same. A producer can raise the price for a product in two ways: 1) directly increase the price for the same weight/volume of product, or 2) reduce the weight/volume of the product while maintaining the same price.
If the company performs #1, a majority of consumers notice, and the company often sees reduced sales (thereby negating the extra profit from the increased price).
If the company performs #2, a majority of consumers will not notice the weight/volume change. Esp. if the outer package is the same size as the prior version, and all that changes is the small "weight/volume" listed on the label. In this instance, most consumers do not realize the price actually increased, and so continue to purchase the same amount as before, but now the company captures greater profit due to the "stealth price increase".
Over time, more and more companies have learned this consumer physiology and are often attempting to hide price increases behind weight/volume reductions. Laws like this are simply an attempt to prevent this stealth price increase and instead make it clear that if the company wants to raise the price of the product, then the price of the product should be what increases. Whether any regulations that result from this statute (should it get enacted) produce that outcome is yet to be determined.
As the act explains, it actually is Coca-Cola's and Heinz' fault that some of the inflation exists, because some of it is just them raising prices to make more profit.
Requiring price increases to be done "openly" will likely reduce inflation, by discouraging price increases.
This should actually be great for companies because it levels the playing field. You don't have to worry that your competitor is going to raise prices by shrinking and look better on the shelf next to you and you never have to change your factory to a new smaller size.
It's good for consumers because it's hard to measure cost of living increases when your grocery bill number stays the same but actually is just 10% less stuff.
So, yes, but also there's other stuff you have to do to ensure that supermarkets don't make this information harder to use/make it irrelevant entirely.
It clearly rubs people up the wrong way.
There's a perception that these huge companies are trying to trick consumers by hiding these reductions in size/quantity. Consumers don't like that.