Both major grading services publish population reports on their websites. These reports indicate how many of each type of coin the service has graded.
It is believed that a low population would indicate the rarity of a coin. However, due to massive over-grading and resubmissions of hundreds of thousands of coins over many years, we believe the population reports are skewed and should not be relied on.
Since we buy and sell almost all CAC coins, the population reports of the two major grading services are of little importance to us. We use them as a gauge only.
If you have read our opinions on grading, you will recall that we believe that at least 80% of coins that do not have a CAC sticker are not accurately graded. Therefore, the population reports for coins without a CAC sticker are irrelevant to us.
We do however rely on the CAC population reports when we buy and sell coins. They are 99% accurate. Coins submitted to CAC for re-grading are hardly ever approved. A CAC re-grade is not a request to increase the grade because CAC does not grade coins. A re-grade asks CAC to approve a coin they previously failed to sticker. Therefore there are no changes to their population reports if a coin fails and then is approved.
If the best coin for a date at CAC is MS67 but there are a few MS68's without the CAC sticker, we pay little attention to them. We believe it is not likely that the MS68's will merit a CAC sticker. Perhaps over time one will, but so far it has not happened too often.
We have been tracking certain coins in the CAC population report over the last year and for the majority of coins a better grade has not been approved.
Sample CAC Pop Report For Buffalo Nickels
Look at the last two lines of this report. If you purchase a PR 1937 in PR68 or a PRCA 1937 in PR66, there are currently only one of each. It it is not likely that more than one or two will ever equal or exceed what you have purchased. You are buying the best coin that exists today!