Perrow's 1994 reply, as quoted by Hopkins, disputes that HRT's flagship systems are complex and tightly coupled rather than arguing they are insufficient
Andrew Hopkins reports that High Reliability Theory (HRT) scholars class air traffic control, power grids and aircraft-carrier flight operations as complex, tightly coupled systems (La Porte & Rochlin 1994), and that "Perrow disagrees." Hopkins quotes Perrow (1994, p. 216) reclassifying each: air traffic control as "basically a linear system," power grids as "quite tightly coupled but moderately linear," and carrier flight operations as "basically linear" and possibly "loosely coupled" because landings and takeoffs "can be easily stopped or delayed." Hopkins's gloss: "Perrow's response is that their work is essentially irrelevant to his because they are studying different types of system."
The move is a scope answer. It contests the input to the theory (which cell of the coupling/interactivity table a system occupies), not the sufficiency of the conditions. That contrasts with claim-la-porte-1996-hrt-accepts-perrow-preconditions-denies-inevitability, where La Porte in 1996 accepts the tight-coupling/complexity description of high-reliability organizations and argues the conditions are "necessary, not sufficient." The 1994 exchange is where the classification was disputed; see also claim-la-porte-hrt-distinguishes-technical-from-social-tight-coupling for the technical/social coupling axis HRT draws.
Caveats: the primary (Perrow 1994) was not read (Wiley returned HTTP 403), so the wording is Hopkins's reproduction. The order of composition of the symposium's Perrow article and La Porte & Rochlin's "Rejoinder" is unverified (Wiley listings only). No quoted passage engages the phrase "necessary but not sufficient"; whether the full article does is unconfirmed either way. Any citation should read "as quoted by Hopkins."
Source
“Air traffic control has been able to reduce tight coupling and is basically a linear system rather than a complexly interactive one. It is not all that clear to me how coupled and complexly interactive power grids are. I judge them to be quite tightly coupled but moderately linear. . . Flight operations on the aircraft carriers are basically linear, and since landings and takeoffs can be easily stopped or delayed, the system may be seen as loosely coupled.”
claude-sonnet-5 · Promotion from 10-inbox/raw/2026-09-24-does-perrows-own-1994-rejoinder-to-la-porte.md, 2026-09-24 · raw markdown