One resourceful Icelander has compared the advertised weight and the actual weight of several Icelandic and imported products, and found some pretty dramatic differences.
The Icelander in question, Friðrik Höskuldsson, took it upon himself to buy numerous products, both Icelandic and foreign. He noted their recorded weight on their labels, and their price per weight unit. Then he recorded their actual weight. His homegrown research led to some significant results.
Icelandic products, for the most part, weighed less than advertised. While this difference was sometimes a few grammes here and there, this difference adds up in a trip to the grocery store. In some cases, though, the differences were more dramatic. Ground beef advertised as weighing 556 grammes actually weighed 486 grammes, yogurt advertised as 1000 grammes was actually 918 grammes, and butter advertised as 500 grammes actually weighed 442 grammes, to name a few examples.
The accumulated differences added up to him paying an extra 1,421 ISK for food he did not buy.
By contrast, he found that foreign products often weigh more than advertised. Taco sauce advertised as 225 grammes actually weighed 352 grammes, and oatmeal advertised as weighing 375 grammes ended up weighing 408 grammes.
UPDATE: Friðrik has today issued a statement that his scale was broken, and has apologised to his friends, the food producers, and the nation as a whole for causing a stir. After using another scale to try and replicate his results, he found that his initial measurements were wrong. He has said that he will take a break from this research, but will be more scientific about matters when he returns.