Of eighteen publishers sizing the psychedelic drugs market, one states its method on its free page.

Most answers to how big the psychedelics market is come from pages selling a report. On 11 September 2026 one reader spent a day looking and found eighteen publishers carrying a market-size figure, which is a floor on what is published and no census of it. Eight of those price psilocybin on its own, and the other ten size the wider psychedelics category, giving psilocybin at most a share or a growth rate inside it.

Six of the eight land between US$1.80 billion and US$4.32 billion, which looks like agreement and is not. Those six attach their figures to different years and differently worded objects, and none of them says what it counted.

The other two fall far outside that band. IndustryARC’s page puts psilocybin at US$62.00 million by 2031 and states no method on the page a reader can open, and Verified Market Reports puts psychedelic mushrooms at US$64.79 billion in 2024 and states no method on its free page either.

The IndustryARC page has a stranger problem: where its segmentation should sit, it lists five product types of gallium, from gallium nitride to gallium phosphide, graded by gallium purity. That is almost certainly a template error on a press-release page, and it is evidence about what a reader relying on free vendor pages is looking at while saying nothing about the report itself.

On their free pages, one of the eighteen states a counting method, two list source types with no base and no assumptions, and the other fifteen say nothing about how the figure was reached. All but one is sold, and a methodology may well sit inside the paid document, but the free page is what every reader of these figures can check.

The one is Market Research Future (opens in new tab), which sizes the wider category and says its estimates

A disclosed method is not a validated one: this is the publisher’s own account of its own work, and it cannot be verified from outside the paid report.

Esketamine is an approved antidepressant derived from ketamine, and it is not psilocybin. A figure built partly on its prescriptions measures something real, but a reader who quotes it as the size of the psychedelics market is quoting a number whose first stated input is a different drug, as the publisher itself discloses.

The method also draws on licensed-centre throughput from Oregon and Colorado, though Colorado publishes a licence register, and a licence is not a throughput.

Five things have been counted, each by a government or a funder, in its own unit and on its own date.

Public money. An obligation is recorded when it is promised and not when it is spent, so a concentration in recent years is partly a fact about how the register records things. NIH RePORTER states US$90,053,627 of extramural obligations across the 133 of 150 project-year records under the narrow predicate that carry an amount, from FY2016 to FY2026, on a read of 7 September 2026, and US$66,709,633 of that falls in FY2025 and FY2026 together: three quarters of everything the register states under the narrow predicate, to date.

Service volume. Oregon reports 5,935 clients served in calendar 2025 and 2,172 in the first half of 2026, a half-year figure this work has not tested for seasonality or for a change in reporting basis and which therefore does not annualise. Each counts clients served in a period, never people.

Licences. Colorado’s Natural Medicine Division register (opens in new tab) carried 44 healing-centre licences at status Approved, held by 43 organizations, on the 5 September 2026 read, and 103 licences of every class: 72 Approved, 15 Pending, 9 Withdrawn, 4 Voluntary Surrender and 3 Denied. Approved is the register’s word for an authorisation and does not mean a centre is open, or has served anyone. A state-regulated service programme is not a prescription, a medicine or a medical treatment.

Permissions to treat. Switzerland issued 322 exemption authorisations in 2024 (opens in new tab), up from 43 in 2021, but a Swiss authorisation counts a continuing patient again each year, so the difference is not a number of new patients. Australia reported 47 new patients through 30 June 2025, from returns prescribers choose to file, and over a different period ending 28 November 2025 approved 36 of 40 prescriber applications. The two do not divide, because the windows differ and an approval permits a prescriber to act while counting nobody. Canada had authorised psilocybin for 50 patients through its Special Access Program as of 4 November 2022, the department’s most recent published figure (opens in new tab).

Kilograms. Governments reported 19.22 kilograms of psilocybine manufactured worldwide in 2024 (opens in new tab), the pure-substance layer reported under the 1971 Convention, which excludes every mushroom grown under an American state programme.

Exactly one thing on this page is shaped like revenue: Oregon’s 15 percent retail tax on psilocybin products under ORS 475A (opens in new tab). It is a rate on product sales, and this work did not read the sales. Oregon publishes product and sales data of its own (opens in new tab), and at least one tracker has derived a revenue figure from it. Neither is counted here, and nothing else on this page stands in for that base.

The registers hold narrow, dated counts that a reader can check and that refuse to add up. The reports offer a single number that adds up, and on the page a reader can open, seventeen times out of eighteen it declines to say how it was counted.