So How Many Of US Are Out There?

As pointed out by both @sel and @kbbpll, frequency is not necessarily a good indicator. I would call a collector who drops, say $5,000 three times a year an avid collector, even though that doesn't meet the current criterion.

I consider myself to be an avid collector for the last 5 years. This year I've averaged 2 coins/month (down from my rate in 2018-2022), but I don;t buy every month; I've bought coins in 9 of the last 12 months.

So I am not an avid collector according to the criterion, but I still consider myself avid.

As for percentages and trends, that's beyond my pay grade, but I suspect somebody has real data (for instance, the auction houses, who must know if their customer lists are increasing or decreasing, ditto for ebay, who would know how many unique IDs are buying coins each year).

Sounds like a good opportunity for a poll.
Though probably the moderators could do a sort on members who have provided a place in their profile and tell us?

The brave few who run this forum have access to georeferenced ISP addresses. That would map nicely--as long as member identities were not displayed.

Estimates of the percentage of the population that are coin collectors varies wildly. These guys claim that their surveying shows 38% of the adult US population "has some experience" with coin collecting - either they currently collect coins, or they used to. A large proportion of that 38% are probably people who collected as kids, but stopped in their teens.

I've seen statistics reporting that between 1% and 5% of the US population would be "serious" coin collectors, by a reasonable definition of "serious" (investing a considerable amount of their free time and/or disposable income). I'd probably guess another 10% are "casual" collectors, who have enough of an interest to know some basic coin facts and actively keep anything odd or unusual that comes their way.

What I do know is, this is not a global trend. The percentage of the population that collect coins is far higher in the US than in most other countries. Canada, Germany and Japan probably come closest. But here in Australia, for example, the percentage of "serious collectors" would be way under 1%.

The nebulosity of the data largely revolves around the assumption of accurate self-reporting (suppose you get a random cold-call survey, asking "Are you a coin collector". Are you going to trust them and answer truthfully?) and the vagueness around the terminology, as can be seen by the debate above regarding the OP's definition of "avid". WHat exactly is a coin collector, and why would any definition we would write be better than anybody else's definition? Lots of people "have a bunch of coins sitting around the place", but we probably wouldn't call them "collectors" - even if they think of themselves as such. Lots of people hunt through change looking for rarities; are they all "collectors", or just bandwagon-jumpers looking to make a quick buck?

I just got back into collecting after a 50 year break, and have been adding a dozen coins and bullion a month.

Collector and stacker aren't necessarily interchangeable. For example my local dealer the majority of customers are stackers, they buy coins but not for numismatic value but for the precious metal value. Over 50% of the customers are bullion purchases. There are a few paper money guys and a large amount of coin collectors. The collectors are many buy purchases aren't as regular as bullion. The dealer recently got a high grade $500 US Note, the buyer paid substantial but that his only purchase so far this year. I go about every month to pick up some bullion coins to add to my stash collection, most are graded and I get different countries so I even my stash is numismatic. That coin shop is one of 5 within a 30 minute drive and all do a brisk business. So we have a pretty large collector base. As to what is collected that changes every year. Peace and Morgan's have been hot last 2 years, prior to that it was Mercury dimes and Lincoln cents. High grade paper has been hot lately. But what he mostly gets in for purchase are pre 1964 silver coins and US Mint products. The good stuff (high grade pre 1950 coins) sell quickly. Once I asked how many people collect and his answer is many, but when you ask for serious collectors he gets 2-4 serious a year. So serious collectors are a little rarer then average collectors. Just making assumptions.

50% of all household have a coin collection.
35-40% collect from circulation
5-10% are stackers
1% are serious collectors

Still over 3 million US collectors.

Looking at ASE as an example there are over 30,000 serious collectors (looking at the price of the 2019 s-erp and 1995 W but you don't see the same price gains for the V75). And ASE are the most collected coins. In the NGC registry there are over 30000 registry owners so heavy duty collectors maybe 10% of the 3 million (~300,000). And many of the 300,000 have deep pockets.

So my guess are:
300,000 hard core/$$$$$ collectors
3,000,000 collectors with fairly extensive collections
10,000,000 stackers
150,000,000 that have a coin collection (maybe State Quarters, some Ike's and a red seal note and silver certificate)

Like others, this rules me out.

I have some "big holes" left to fill, so those will take time. Otherwise, I am at the mercy of the US Mint release schedule.

As for the question... If my own circle of friends and family are a diverse snapshot of North American society (and they seem to be, given the, uh, "robust" conversations at gatherings), then I would say the ~1% estimate is accurate. Anything approaching 5% seems unlikely.

Of course, that is not a scientific poll and your mileage may vary.