Size ranges

[happytraveler]

From searching for stones that score well on the HCA, I noticed that the .91-.99 ct range is really empty.. Are people just snatching these up really fast?

Also, I had a retailer in Chicago tell me that around 1.25 ct is a "difficult" range to find stones. Why would that be?
Thanks!

 

[chialea]

There are a few reasons I've heard mentioned for the phenomenon. Firstly, people do snatch them up really quickly. Secondly, cutters often have a choice between a .9x ct ideal cut diamond, and a 1.0x non-ideal (or close to ideal) cut stone... since there's such a huge price jump at 1ct, it just doesn't make financial sense to cut those diamonds like that -- those .9x ct ideal cuts often take more time to cut, and they don't make as much money as they could on them.

 

[happytraveler]

Thanks, that makes a lot of sense.

I just wanted to say thanks to Leonid for putting together this site and the philosophy behind it.

On a sidenote, I'm an engineer and enjoy math - I've been able to reverse engineer within 3% tolerances some vendors' pricing models. If anybody cares, you can set up a General Linear Model similar to designing experiments with Six Sigma and Taguchi methods. It will give you correlation coeffecients that show how a vendor values certain factors.

 

[WinkHPD]

I have no idea what you just said, but reading it makes my head hurt!

Wink

 

[Regular Guy]

HappyTraveler,

Can you give an example? Are you saying, for example, that this shows you the % valuation that is given to functions like color vs. clarity?

 

[MelanieC]

I agree with Wink. That might have well been posted in another language. It went way over my head!

I definately don't see too many in the right under 1ct range. When I was buying my diamond though, he had a .98 F SI1 that he had just got in and was waiting on the Cert so I couldn't see what the measurements were. I ended up going with a 1.08ct diamond instead.

 

[happytraveler]

Sure -

I apologize in advance to the people that this is likely to bore!

If you look at a bunch of diamonds from one vendor, you guess at their formula. They might price by adding a % of what they paid for the diamond, or they might try to use a formula to price their diamonds "smarter" than the formula that their wholesaler used. This would take into account some or all the determinents of value.

Maybe every time you drop a color grade, you guess that the price per carat will drop by X dollars. That's linear. And everybody already knows that all things equal, doubling the weight is more than doubling the price. So maybe that's a square factor, or maybe exponential.

When the analysis is done, you can say in statistical terms how much value, in price per carat, a dealer (or the market) places on a factor (color, clarity, even flourescence). That's the correlation coeffecient.

The next test is the variance of the correlation coeffecient. That sounds complex, but it's just telling you how often the diamond specs you fed into it fit your model well. All other things equal, if a color upgrade from G to F sometimes is worth $100, sometimes $400, sometimes $600 - then that vendor isn't using a highly predictable system, or a system at all. You'd have a very high variance on your correlation coeffecient.

When you feed a General Linear Model a bunch of data, it's really good at taking a bunch of "orthoginal factors" and pretending like you had only changed one thing at a time, even though maybe each of the 500 diamonds you analyzed changed 2, 3, or 4 factors at a time. Color and clarity are probably orthoginal factors in their middle regions.

These Taguchi methods are why in the 80s, import cars got a reputation for being higher quality than domestics. Mr Taguchi was helping Japaneese makers find out that when they changed one thing (maybe size of a brake pad), it failed a lot less. But they only had to make a few cars that changed a bunch of carefully chosen things at once - and they were able to infer a lot of useful data that made them more reliable.

 

[Lynn B]

Oh lord! I read it twice, and still don't get it! May as well be another language!

Doesn't matter to me personally anyway, though, I already bought my diamond. But if any of you still shopping are interested in all that, I say, go for it!

Lynn (aka Math Moron)!

 

[pqcollectibles]

Those are 2 highly desireable carat weight ranges, 0.9-0.99 and 1.25, and they go quickly. If you're interested in diamonds in either size range, you might try sourcing thru a Vendor to look for you, and be prepared to wait until the right diamond comes along.

As far as pricing, I like Paul Slegers explanation better.

"If you take the basic price of I-SI2 at a ratio of 100, then an I-SI1 is about 115, an H-SI2 is about 111 and an H-SI1 is about 130. Therefore, you cannot directly compare an I-SI2 with an H-SI1. The second one has inherently a 30% higher price, so if you get the I-SI2 at the same price, you are paying a premium of 30%."

https://www.pricescope.com/community/threads/would-you-buy-a-hof-diamond-if-it-was-only-5-10-more-should-i.16958/

Much simpler to understand.

 

[icelady]

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On 7/13/2004 5:12:26 PM happytraveler wrote:

On a sidenote, I'm an engineer and enjoy math - I've been able to reverse engineer within 3% tolerances some vendors' pricing models. If anybody cares, you can set up a General Linear Model similar to designing experiments with Six Sigma and Taguchi methods. It will give you correlation coeffecients that show how a vendor values certain factors.----------------

Six WHAT? and Hoochie Mama? Methods? Whoa, way over my head!

 

[noobie]

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On 7/13/2004 8:54:51 PM pqcollectibles wrote:





Much simpler to understand.

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Yes PQ, but I'm still pretty sure that you understood his statistical analysis description perfectly

 

[pqcollectibles]

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On 7/13/2004 9:12:22 PM noobie wrote:

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On 7/13/2004 8:54:51 PM pqcollectibles wrote:



Much simpler to understand.

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Yes PQ, but I'm still pretty sure that you understood his statistical analysis description perfectly

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Ssshhhhhhhhhhhhh, Noobie!! The "Dumb Blonde" routine has worked for me so far. I don't wanna blow it!!