In the last 3 years, in Minnesota (US), bearing in mind that the minimum temperatures in winter have decreased, the difference in the weight of marketed pigs between summer and winter...

The correct answer is that the difference has decreased. One of the more interesting things to observe is that in the last three years, the average annual minimum live weight has been increasing even though the average low temperatures in winter have been falling. Summer weights have remained very stable over the same three years. This suggests that increased control is being exercised to manage weight variation and respond to optimal weight marketing