We do it regularly by zip code. Then it's possible to build a grouping of Zip Codes until you have an entire region. The problem is NOT using registration data. It's necessary to find supply and demand through surveys about a ll spending, not just car intender spending. That may see a bit more complicated, but it's the only way to make sure the data is correct.
Some trucks are still a seller's market.
It also depends on the region of the country. But generally, buyers have the upper hand. Just to follow up on those two question. The best way is to watch classified ads. If classifieds from dealers as well as from individuals seem to be growing, then the market is a buyer's market.