I want to know the answer to the following question:
how much of the population have the rural plains lost since 1920?
All the background I'm provided with is that "The continuing population loss has led some to suggest that the current use of the drier parts of the Great Plains is not sustainable, and there has been a proposal - the "Buffalo Commons" - to return approximately 139,000 square miles (360,000 km2) of these drier parts to native prairie land.". Is that enough to answer the question?
Answer: no