If anything car prices are effected by inflation not the other way around. The biggest factor currently inflating used car values is a shortage of new cars due to chip shortages and other logistical issues. People need to buy cars and with a shortage of new cars on lots, quality used cars become more valuable
In the U.S. sales data gets reported as part of the title transfer process. Even for private sales.
Titles include a tear away portion for record keeping and documenting the sale. The sale price must be listed on the title when the new owner submits it to the state for transfer and issuance of a new title with their name on it.
The tax owed by the buyer is based on the price written on the title. So its not uncommon for private sales to actually purchase at one price and list a lower price on the title to reduce the tax bill (this is illegal). It can’t be too lowballed or the state will flag it for investigation.
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