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Question: How To Estimate Surviving Population Of Old World Coin?

 
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Author Previous TopicReplies: 8 / Views: 320Next Topic  
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 Posted 08/01/2020  09:15 am Show Profile   Bookmark this topic Add thegrendel to your friends list Get a Link to this Message
I just bought an 1892 South Africa penny on eBay. Mintage is 83,000, so I guess it's pretty rare in the general scheme of things. I'm wondering how many of these babies have actually survived. I don't imagine too many were saved back in the day, so I guess an off the cuff estimate might be maybe 10%, or 8,000 or so, which would make them pretty rare. Am I way off base? What say ye?
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 Posted 08/01/2020  11:32 am  Show Profile   Bookmark this reply Add tdziemia to your friends list Get a Link to this Reply
I will be interested to hear others' views on your question.
Or even whether there have been attempts to do these kinds of estimates/calculations.

But here's my take:
- A quick look at the NGC census shows 1,243 examples have been graded, another 239 at PCGS, for 1.8% of the total mintage graded.
- An eBay sold items search shows 14 examples sold in the last 90 days, 13 raw and 1 slabbed (13:1 ratio).
- Coin archives shows a 6:1 ratio, but of course the population in that database would be skewed toward slabbed coins

I think it's more likely that upwards of 20% of these have survived.






Edited by tdziemia
08/01/2020 11:34 am
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 Posted 08/01/2020  10:51 pm  Show Profile   Bookmark this reply Add Numister to your friends list Get a Link to this Reply



We'll need a Coin Cerebro.
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Australia
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 Posted 08/02/2020  07:55 am  Show Profile   Bookmark this reply Add Sap to your friends list Get a Link to this Reply
Guessing survival rates of any coin is difficult. Guessing survival rates of coins issued by an extinct country is even harder. Many of the ZAR coins would have been actively withdrawn and destroyed by the British after they won the Boer Wars. I doubt that any specific records of the destruction would have been kept. Many of the surviving coins were turned into "Shawl pennies", the ZAR equivalent of "hobo nickels". Silver and gold coins suffered a similar fate, probably to an even more extreme degree as precious metals are far more readily recycled into new coin than bronze. The ZAR veld pond, for example: more than 50% of the known surviving examples are either mounted as jewellery, or ex-mount damaged.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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 Posted 08/02/2020  08:32 am  Show Profile   Bookmark this reply Add thegrendel to your friends list Get a Link to this Reply
An interesting and informative response, Sap.
Sounds like a topic for a PhD research paper.
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 Posted 08/02/2020  08:42 am  Show Profile   Bookmark this reply Add tdziemia to your friends list Get a Link to this Reply

Quote:
We'll need a Coin Cerebro.

Not gonna try to claim that title, but what I did was take the ratio of raw coins to slabbed coins in one known population (13:1), then apply it to the known total slabbed population to get an estimate of the surviving population. That makes one big assumption, namely that the eBay sold items population over a narrow time window is "representative" of the population of surviving coins. I would feel better about that assumption if there were something like 100 or 1,000 coins, not 14.


Quote:
Many of the ZAR coins would have been actively withdrawn and destroyed by the British after they won the Boer Wars.

I had that same thought, but I also wondered if some might have been saved for nostalgic purposes by the non-British population. Though I suppose it would have made more sense to save silver.


Quote:
Sounds like a topic for a PhD research paper.

Already done for non-obsolete series: https://www.researchgate.net/public...oins_Carried
The trick would be how to adapt these results to a case with a discontinuity like this.
Edited by tdziemia
08/02/2020 08:51 am
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 Posted 08/02/2020  12:02 pm  Show Profile   Bookmark this reply Add oriole to your friends list Get a Link to this Reply
For non-obsolete coins, the CCF may have some excellent information-just go to the roll hunting forums. Based on what is found in circulation, what % have been lost/ hoarded after a certain number of years.
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 Posted 08/03/2020  12:39 pm  Show Profile   Bookmark this reply Add thegrendel to your friends list Get a Link to this Reply
>> The trick would be how to adapt these results to a case with a discontinuity like this. <<

It's an interesting article, but I'm not sure it applies to the original question. Phenomena with large sample sizes do tend to more or less be described by a power law or inverse power law -- a mathematical curve. But if you're dealing with a mintage of a few tens of thousands then it is indeed correct to describe it as discontinuous, or at least somewhat unpredictable. What it pretty much comes down to is "my guess is as good as yours."

I've learned a lot from this thread, and I thank all who took the time to respond.
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 Posted 08/03/2020  2:41 pm  Show Profile   Bookmark this reply Add tdziemia to your friends list Get a Link to this Reply
By discontinuity I meant that the series was discontinued over 100 years ago. The research paper was written for coins that are still in circulation. SO, you could have applied it to the number of surviving coins in 1898, but then as pointed out by @Sap, you would have had that coinage replaced by the British coinage. That's not a circumstance that's modelled in the paper.

I agree with your final conclusion ... but there is evidence it's higher than 10%.
Edited by tdziemia
08/03/2020 2:42 pm
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