Searching the Internet Archive’s scanned book corpus for the phrase returns a tight, telling cluster: leadership manuals, sales and network-marketing books, supervisor handbooks, trend-forecasting guides and devotionals. Nearly every one of them prints the line beside Mead’s name and no page number. One education title, Marilyn L. Grady’s 20 Biggest Mistakes Principals Make and How to Avoid Them, does give a citation — but it cites “(Maxwell, 1999, p. 51),” pointing at another quote-repeating business book rather than at Mead.
The wording itself is unstable, which is the usual fingerprint of a saying that travelled by mouth and by handout rather than off a printed page. Two versions circulate — “what they say they do” predominates, but “what people say they do” runs alongside it in the same scanned-book corpus. A sentence lifted from a specific published paragraph tends not to drift like that.
None of this proves Mead never said it — she lectured constantly, and an unrecorded remark leaves no trace. It does mean that after decades of circulation, including a formal search by Harvard reference librarians, the quotation still has no anchor. Until one turns up, the honest label is “credited to” rather than “said by.”