When i was in a car auction i talked with a guy next to me and he was writing down all the information of the auction. He told me he worked for a close by dealership and those numbers were used to decide on the trade-in values they could offer (as worst case the car would end up on that auction)

Today i was checking a price in one of the many sites that offer market values for cars/motorcycles. And their site mentions that they do research in auctions as well (public price) and also says

Consumer Private Party Transactions

Kelley Blue Book tracks consumer sale prices each year.

from http://www.kbb.com/car-advice/articles/what-are-kelley-blue-book-values/

How exactly do they get that? Unless the buyer or the seller report the transaction value to the company, how else can they get this data? Does the government sell private citizen financial information? Do they contact a few people and extrapolate (like TV ratings)?

And where can i find out more about also accessing this information, assuming it's public?

3 Answers 3


Does the government sell private citizen financial information?

Of course not. The government sells public citizen financial information. That includes everything on your registration forms other than your SSN/Address.

When you register car or transfer the ownership, the price is reported to the DMV (among other things, for assessing the sales tax). Thus, it becomes a public record, which data mining companies like KBB have access to.

  • I'm pretty sure your tax reports aren't public like that.
    – gcb
    Aug 15, 2013 at 18:37
  • @gcb who said anything about tax reports? I'm talking about the vehicle registration.
    – littleadv
    Aug 15, 2013 at 18:40
  • so you are saying the vehicle registration data that you submit to the DMV are public? That's VERY far from the official word: dmv.ca.gov/portal/portal/policy.htm further, the sale price is not even listed as the type of information that is archived by the DMV during registration dmv.ca.gov/dl/authority.htm#register
    – gcb
    Aug 20, 2013 at 23:00
  • 1
    @gcb BTW, in case you didn't know that - the vehicle registration fees the CA DMV charges you every year include a tax portion. That tax is calculated as a direct percentage of your car's value (1.2%, if I remember correctly). In the first year it is based on the reported sales price, they use a formula to depreciate it after that.
    – littleadv
    Aug 20, 2013 at 23:45
  • 1
    @gcb yes. For California for example see here: dmv.ca.gov/portal/customer-service/…
    – littleadv
    Oct 10, 2022 at 18:19

From the link in the question:

Kelley Blue Book representatives audit these auctions on a regular basis to gather a better understanding of what the highest possible "actual cash value" of a given used vehicle will bring at auction.

Thus, they may have representatives at the auctions that record the transactions. If there is someone present at the auction, they may record the prices and thus this could be reported back. After all, if one witnesses the bids, these could be listed. This data could then be extrapolated like TV ratings.

Something else to note from that link:

Used values are determined by a proprietary editorial process. This process starts with a thorough analysis of all collected data along with historical trends, current economic conditions, industry developments, seasonality and location. The resulting values reflect the most current representation of a changing marketplace and are therefore relied upon by a variety of leading organizations as well as the average consumer.

Thus, there can be some massaging of the data they collect which isn't publicly known and thus it isn't just the data coming in that is used but rather there is something to be said for various factors influencing things as I'd imagine car prices in a big city may differ from a small town on some levels.

  • The auction part is clear. As i saw for myself, the sale price is public there. And what they do after they have the data does not help to figure out how they got it :-/
    – gcb
    Aug 15, 2013 at 17:23
  • The second quote notes that they have their own custom process for taking all the data and sifting through it. It wouldn't surprise me if they had some actuaries that help interpret the statistical data. This is the part that isn't public and for good reason as otherwise some may game the system similar to Search Engine Optimization stuff.
    – JB King
    Aug 15, 2013 at 17:30
  • Still can't see where they hint at where the data cames from. Also, everyone knows how a search engine rate links and pages. most of the algos are patented and/or have white papers, so you can simply read it.
    – gcb
    Aug 15, 2013 at 18:39
  • While everyone knows that search engines rate links and pages, the specific details aren't public knowledge. How many people study ways to try to outsmart Google? Or is there some white paper of how Google ranks everything out there that I don't know?
    – JB King
    Aug 16, 2013 at 3:46
  • yep, it's not even public but they go great lenghts to document it, as it's their best interest you follow it. You are thinking about abuse control, not how the ranking works. e.g. how to detect if one site is just a copy of another one. Not how the valid sites are ranked up, that's pretty clear.
    – gcb
    Aug 20, 2013 at 22:58

KBB, NADA, Black book and all the others have no idea what an actual price of a used car is. Registrations that are public information shows the taxable amount, the amount you paid for the car less any trade. Therefore if you purchased a $40,000 car and had a $20,000 trade that vehicle would be evaluated as $20,000 retail. That really throws the figures in the toilet, which is where the books should go.
If the books were accurate the banks would not loan over book value for a car, some loan up to 150%: (try to buy a house for 150% of appraised value). Shop different lots, look at the reputation of who you are dealing with, most cars these days are sold for the advertised price, not the book value. Remember next time you look at a book value, ask that company how they came up the value, you cannot get a straight answer, they will tell you it is a proprietary evaluation, really?

  • where can i get public registration information?
    – gcb
    Jul 8, 2015 at 14:34

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