The atlas's own cited source lists a 1997 scholarly treatment of the movement titled "The Rise, Fall, Rise, and Fall of the Manchester School" and separately reports a 2025 commentator invoking the live label "Manchesterism," together describing a movement that its own historians do not treat as ending at one clean date. No single end-year is stated anywhere in the cited source.
What would resolve this Reading the cited Bresiger 1997 article itself, or a comparable secondary treatment, to see whether it names the specific dates of each rise-and-fall phase would let this atlas either attest a genuine end-year or record the cycles explicitly instead of leaving the question open.
Openhistory of economic thoughtManchester Liberalism (Wikipedia)