Bring back authentic values

I noticed recently that for a lot of types and year lines the values for multiple grades in a row are suspiciously identical. As far as I can tell this is probably due to the long-suggested option that lower values in higher grades were to be artificially replaced if there's a higher value in a lower grade.

(I might be entirely misunderstanding; there's nothing about it on the forum. If so, please provide the actual explanation.)

I liked the previous system much better. It gives actual information and not an artificially smoothened-up version. Values in lower grades can be naturally higher for a type collected by lowball collectors (some NIFC types are scarce even in F-VF grades), or more commonly they can be artificially higher because the owners of a lower-grade example are mostly foreigners who didn't realize how common the higher grades were; in either case they have no relation to values in higher grades.

If a coin is valued at (for example) 3 euros in VF and 2 euros in XF, I want to know that, even if it looks like a bug - in particular, in either of the above two cases, the lower XF figure probably has a lot more data behind it, and the higher figure in a lower grade is either an artifact of missing data (from owners who don't bother to enter prices for their common coins into Numista) or a legitimate representation of grade rarity. If instead the page is “fixed” to say 3 euros for both, this ignores all the data pointing toward a 2 euro price in XF.

Commentary welcome. If you think this is stupid because of something I didn't think of, say so. The downvote button exists for a reason.
…I would obviously prefer more upvotes, obviously, but I want a honest opinion.

Hello,

I confirm that prices are adjusted in case a value for a lower grade is higher than the value of a better grade.

If such situation happens, both grades get the same value, which is computed from the values for both grades and weighted by the amount of data available for both grades and their freshness.

I don't know any case where a coin in a lower grade is less valuable than a coin in a better grade, even if lower grades are rarer (which is the case for many non-circulating coins for example). So I believe it makes sense to identify cases where the values are inconsistent and use more data to compute the value (using data for both grades) to get a more accurate value, even if it means we lose granularity per grade.

See an example for N#355, where data from grades XF and AU were merged and result in the same value for both grades:

January First-of-May

… from owners who don't bother to enter prices for their common coins into Numista) …

Wait, what? How does one do this? Is this what the “Buying value” box is for?

Are the coin values just an average of what Numista users type here?

@Ben-jamin 

What else would it be for?

Personal use and not used in site-wide calculations?  I also had the impression it was just for your own bookkeeping.

Those are the values used to calculate the values in the year lines along with auction/sales result, etc. There are several recent posts where the method is fully explained.  I’m stuck on my cell right now. When I get to my PC I’ll post the links unless somebody beats me to it. 

Per Xavier:

Here are the rules for calculation.
 

1. Values are computed by type, year/variety and grade
    
2. A value is calculated only if at least 4 users entered a price for their coin
    
3. The value is calculated as the median of the values entered by the users
    
4. If a user entered several values, a median of his values is calculated and only the resulting value is used for the median calculation of step 3.                                                                                                                                                                                                                                                                                                     
5. Calculations are done in euro. Values entered by the users are converted in euro at the time they are entered. The display of the calculated value is converted to the user's currency at display time.
    

Question though, If I indicate that I have a “quantity” of 5 coins, the “Buying Value” should be the cost of all 5 coins, right?

 No. The value of one coin. 

Otherwise the value would be five times as high. 

Giving a false value. Example: 

Five coins costing $2 each, so total $10, would have $2 entered. 

It seems plausible that in some cases a bit of valuable information is lost due the smoothening of values, however, are such cases common?

Anyway, it would be nice to have a button on every coin page for turning the smoothening off, so that everyone could decide what information they need.

Yet another solution (which is implemented by a Numista's “competitor”) would be to show the raw data to which the formula is applied.

The algorithm to compute prices has actually become a bit more complex than the explanation above, in order to give a bigger weight to recent values. Past auction sales (mainly from Heritage Auctions and Katz for the moment) are also taken into account.

Showing the raw data is only possible — and done — for past auction sales. I can't show the buying price from personal collections, as this is private data.

I see!  Thanks all.  I believe then, I will stop putting in values when I buy bulk lots of coins.  I'd been dividing the price evenly among the number of coins.  Sounds like that's bad data going into the system.