Having been a member of this site for quite some time, and having a long conversation with a friend yesterday, I realized that I could not completely explain the Rarity Index.
I started at 100- no one has it
97- 1 person has it
Then no idea. Anyone have a definitive list, say down to 75 or so, but appreciate any list which I can keep for my own records and show my friend
Interesting reading, but it does not answer my question.
A certain number of collectors must own a coin with say, a rarity index of 90, but, how many????
The same must follow for all of the other index figures, so somewhere there must be a list within the computer system so it can change the rarity index if a new collector adds a coin to his/her collection, thus causing a rarity index change.
I used data of the number of users owning a coin with a one year line coin page (of my countries), so there was a limited amount of data points but I think it is reasonably accurate (as long as the logarithm didn't change in the last couple of years).
But like Xavier stated there is probably a bigger deviation in reality.
For example, it shows about 7 owners for NRI=90, which matches my example above.
For NRI=30, it shows about 210-220 owners, which is true if 20% of the owner offer the coin for swap.
Here is the graph of Numista rarity index depending on the number of owners, with the assumption that 20% of the members who own a piece of the coin type offer at least one of their coins for swap.
I need to find a coin I own with a rating of 97, then at regular intervals, add one, then two and so on to my swap list, and wait for the rarity index to change on the system. I can then create my Rarity Index list
Exactly how long does the system take to catch up in changing the rarity index?
The rarity index doesn't depend on the number of coins you add, it only depends on the number of members who have the coin and the number of members who offer the coin for swap. You'd better use the graph provided by Idolenz or the graph I provided above.
Just a thought about changing the name to something more accurate/appropriate.
Having read quite a few comments about the NRI, it seems one of the criticisms is that it does not necessarily reflect the true rarity of the coin in the broad numismatic market, only among Numista members.
From the link in the second post: The Numista Rarity Index is computed from the number of members that have it in their collection and the number of members who offer it for swap.
Those numbers are frequencies. Hence “member frequency index” is more descriptive (and less open to mis-interpretation) than “Numista rarity index.”
“Member Rarity Index” would also be better in my opinion, because it's more explicit about what “rarity” pertains to. But MRI is a common acronym for something else in English (a medical procedure)
That's the result of an engineer considering the matter … Maybe it doesn't make sense to most of the world 🙂.
How can anyone think that Numista Rarity Index wpuld be applyable anywhere outside of Numista? The clue is in its name. It's NUMISTA Rarity Index, not the Rarity Index of the While Numismatic World. That would be RIWNW.
Just a thought about changing the name to something more accurate/appropriate.
Having read quite a few comments about the NRI, it seems one of the criticisms is that it does not necessarily reflect the true rarity of the coin in the broad numismatic market, only among Numista members.
From the link in the second post: The Numista Rarity Index is computed from the number of members that have it in their collection and the number of members who offer it for swap.
Those numbers are frequencies. Hence “member frequency index” is more descriptive (and less open to mis-interpretation) than “Numista rarity index.”
“Member Rarity Index” would also be better in my opinion, because it's more explicit about what “rarity” pertains to. But MRI is a common acronym for something else in English (a medical procedure)
That's the result of an engineer considering the matter … Maybe it doesn't make sense to most of the world 🙂.
tdziemia - The member frequency index” sounds good.
I like this suggestion - “Member Rarity Index”. Shortened to MeRa - in Hindi (मेरा) this means mine.
Many people equate "rarity" with "value" particularly confused new members looking only to know what they can sell their coin or note for. If it were renamed to Numista Ownership Index (NOI) (where NOI = 100 - NRI) it would be less confusing and more obvious what it meant. A coin with a high NOI would imply it was a coin that was desirable to most collectors without a cogitation of low value. Just a thought....
How can anyone think that Numista Rarity Index wpuld be applyable anywhere outside of Numista? The clue is in its name. It's NUMISTA Rarity Index, not the Rarity Index of the While Numismatic World. That would be RIWNW.
🤣 +1
Wanted & swap list (euro coins & world coins, exonumia and banknotes circulated) https://goo.gl/AQjfKp - I have euro & world CC coins for swap.
How can anyone think that Numista Rarity Index wpuld be applyable anywhere outside of Numista? The clue is in its name. It's NUMISTA Rarity Index, not the Rarity Index of the While Numismatic World. That would be RIWNW.
I would take “Numista Rarity Index” to mean “the rarity index assigned to a coin by Numista," rather than “the rarity index only valid within Numista.”
We are positioning ourselves as a numismatic reference catalog. Other catalogs use R, RR and RRR or R1, R2, R3, and so on to indicate the relative rarity of a coin. It would be very easy for a user to assume that our NRI is this kind of scale.
Until they go looking for the definition or a thread like this.
