Adding sales data

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minitw
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Joined: Wed Sep 26, 2012 11:58 pm

Adding sales data

Postby minitw » Sun Jan 20, 2013 11:33 pm

I want to float this out there, but is there a way we can come up with a system where members can add sales data from cameras sales they observe? I know there are lots of issues such as abuse, quality control of the data, etc, but at the same time it's hard if only one person is in charge of adding everything. Naturally, there are thousands of cameras out there and it's unrealistic to ask one person to be in charge of it all. By opening it up to everyone to add this will add value to this forum because we'll have more up to date sales data.

diser
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Re: Adding sales data

Postby diser » Mon Jan 21, 2013 10:40 am

Minitw, thanks for a suggestion! Here is my intake on this, and why I usually don't add eBay sales to calculations:

The algorithm calculates a camera value by checking previous sales, item condition, and date of sale. After price, the most important item here is condition. Some auction houses don't list it, making it hard to put a camera in a bin with proper price range; those I don't consider. eBay sales are not added due to sellers using words like "camera is in excellent condition considering its age" or camera is "Ex-", for cameras that are clearly below average, or some could be considered in a poor condition; I bet you have met listings like this :cry: I don't trust those valuations from non-expert sellers, so I try to use values only from consistent valuators, and those usually come from a handful of hammer auctions. Moreover, I found that some auctions rate items usually on a higher end than others, so algorithm takes that into account, normalizing their valuations too. If you know about other auction houses with proper valuation system, let me know, I'll add those for sure!

Another way to get a proper condition is a personal experience. Let's say you purchased a camera on eBay, which was listed in excellent condition, but it was C+. In this case you know the actual condition :!:, and your voice can definitely be trusted unless you abuse the system. I was thinking of using those conditions/prices looking at folks' "camera inventory" data. As you can see, it has fields for price, condition, etc. But at the end it became not that obvious, so I dropped the idea.

And yes, from time to time I am getting back to thinking about using prices from as many sources as possible, especially site's knowledgeable members, and thinking about what you said. What still concerns me is item's condition, and I wasn't able to come up with the solution of considering it in a proper way. If you have some ideas, let's discuss it! :)

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John Kratz
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Re: Adding sales data

Postby John Kratz » Mon Jan 21, 2013 2:38 pm

You're right, Eugene - it's nearly impossible to get everyone to use the same condition grading scale. I'm sure you've seen the scale proposed/used by McKeown. That's a great scale which leaves virtually no room for misinterpretation, but very few people actually use it.
Also, in my particular case, I don't use the cameras I buy for my collection, and so the functionality part of McKeown's scale doesn't come into consideration for me - I'm only concerned with cosmetic condition. Of course, other collectors are primarily concerned with functionality and don't care as much how nice a camera looks. So even if you use a simplified scale, like one to ten, one person's "five" could obviously be very different from another person's five.
Have a look at some of the cameras in my collection:
http://collectiblend.com/Cameras/mycamprofile.php?uid=396

minitw
Posts: 112
Joined: Wed Sep 26, 2012 11:58 pm

Re: Adding sales data

Postby minitw » Mon Jan 21, 2013 3:18 pm

I completely understand all the challenges in regards to accurately evaluating the condition and how things are misleading on eBay and how everyone has a different scale to evaluate condition. I wish I had a good solution, but right now I don't either. :| I guess one frustration is when you go to the pages of some cameras and the last sales data is 10 years ago when there has been a lot of more recent sales. It is a complex thing though and I wouldn't want to all of sudden let everyone start adding and then all of a sudden we have a bunch of garbage data either.

Maybe this is something we can split into groups of sub administrators based on what cameras people mainly collect. For example, I like to collect Tower Pentax and Asahiflex cameras so if people see things related to these cameras they can e-mail me and then I would filter through the sale and then make a judgement. Of course this would require the sub administrators to be trained on the same quality judging scale.

A very complex problem, but I will keep thinking of some ways we can possibly do this while maintaining accuracy of the data.

diser
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Re: Adding sales data

Postby diser » Mon Jan 21, 2013 3:22 pm

John, thanks! That's another great point I've seen even with hammer auction results. Some auctions base their grade on a cosmetic condition only. So, for these auctions, if I see a camera sold in a "good condition" but with non-working shutter, I usually drop the condition by a grade or two before adding it to the database. The grades are so subjective...

McKeown's approach is great, I like it. It could be a good idea to allow adding a camera price, as minitw suggested, but strictly adhere to the cosmetic+functional grades, clearly listed on a site. Though looking at some eBay sales, I wouldn't even try to grade cameras with those blurry photos and bias descriptions :roll: So, a persons' integrity (which adds a price) should be "a must", as minitw addressed in the original post.

Adding a field for the price source (like a link to ebay sale) may be an option, so one could moderate/review the new prices before introducing them to a database.

minitw, sub-administrators is a good idea, thanks! Let me chew it over for a few days :)

minitw
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Re: Adding sales data

Postby minitw » Mon Jan 21, 2013 6:44 pm

Also, I am curious ... when an auction like Westlich finshes does the system automatically populate the sales, or does it have to get manually fed in? I was looking at some past Westlich auctions and there were instances where the sales were not reflected in Collectiblend.

diser
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Re: Adding sales data

Postby diser » Mon Jan 21, 2013 9:35 pm

Auto-populating never works, in many cases I need to consider serial number, double-check the camera name (sometimes there are a lot of mistakes), etc. So, I manually add sales results.
If the sale is not reflected, usually this meas one of these things: camera had more than one lens with it; camera had a lot of accessories; several other same cameras were already sold on this day by this auction (look at Leica IIIg - I stopped adding every single sale, adding one or two per auction/day). Also, in the case of WestLicht, I think a couple of early auctions (#1-4?) had wrong dates/months listed on their web-site earlier, so those are in DB as they were before. PM me the camera name and auction date, I'll let you know why it's not in the DB :)

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Madd10
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Re: Adding sales data

Postby Madd10 » Wed Jan 23, 2013 5:26 am

Is it possible to modify collectiblend so that you encourage people to enter Ebay sales.

You could maybe force people to enter data in specific fields whereby they have to post the Ebay picture, the exact text from the Ebay description as well as the price and date. In this way you capture the 'objective' Ebay information that anyway Ebayers use to determine what price they are willing to pay. A link might be useful but I believe that this link will probably not work after a couple of months as Ebay removes old sales.

If you want, you can then analyse these results later and come to a more objective classification which you capture in a summary table for Ebay sales. You could have the analysis done by one person or ask a number of people to provide ratings to try to 'ojectivise' the results. Ebay is simply an important sales channel so I do think there is value in trying to capture it.

I am not so sure how to capture data of cameras being sold on collector's fairs but maybe a similar system would work as well whereby people put their own descriptions, pictures, purchase date and location on the site and later have the data analysed and summarised in a similar way.
Interested in seeing what I am collecting ? Check out my camera collection:
http://collectiblend.com/Cameras/mycamprofile.php?uid=988

diser
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Re: Adding sales data

Postby diser » Sun Jan 27, 2013 10:10 am

I have added this functionality and after some testing I believe it works fine.
Please check the "Add another price source" link at the bottom of the "Camera sales" list on each camera page.

While I am still working on injecting the newly added prices into the camera valuation algorithm, you can try adding some prices already. They will become a part of the calculation soon.

Madd10, Even though it does not allow to add images from eBay (because of copyright issues), it does allow to add date, price, cosmetic and functional condition, as well as a link to the price source (or some comments).

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Madd10
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Re: Adding sales data

Postby Madd10 » Tue Jan 29, 2013 12:47 am

Seems to work fine - I think it is a great addition.
Interested in seeing what I am collecting ? Check out my camera collection:
http://collectiblend.com/Cameras/mycamprofile.php?uid=988


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