The "insiders are selling 10 to 1" statistic
Widely circulated this month · the measurement itselfSingle-source ratio
The August 2026 insider sell-to-buy ratio was reported at roughly 10:1, described as the worst month of the year; first-half 2026 saw a record $77.6bn sold against $6.9bn bought, about 11:1.
Consensus read
The people who know their companies best are selling at a near-record pace and barely buying. That asymmetry is a warning about valuations, and the widening ratio through the year tracks the market's ascent.
Contrarian read
The ratio cannot measure what it is used to measure, because its denominator is not a decision. Insiders are paid in stock and must sell to convert compensation into money; there is no corresponding mechanism that pays them cash and requires them to buy. The numerator is compensation mechanics plus sentiment. The denominator is sentiment alone. Dividing the first by the second produces a number that rises whenever share prices rise, regardless of what anyone believes.
Evidence that discriminates
Look at what is actually in the denominator this window. The two largest open-market purchases above $1m in the 10–14 September filings were Larsson's engineered $1,000,001 and a $1,052,415 purchase by Donegal Mutual Insurance in its own affiliate, Donegal Group — a structural intra-group purchase. When a ratio's denominator is composed of one deliberate signal and one related-party transfer, the ratio is not measuring belief.
The numerator is mechanically price-elastic. The same number of vested shares sold at a higher price produces a larger dollar numerator with no change in behaviour. A "record $77.6bn sold" in a year of record index levels is close to arithmetic. This is the fact the consensus read cannot accommodate: it treats a price-scaled quantity as a sentiment measure.
The better-constructed version of this indicator exists and says something different. Practitioners who use insider data seriously count discretionary open-market purchases by number of distinct insiders, not net dollars, precisely because dollars are contaminated by compensation and price. Any ratio quoted in dollars, with no separation of 10b5-1 from discretionary, should be treated as a headline rather than a measurement.
Honest limit: I have the September ratio quoted as improving to 3.6:1 from a single source and could not independently verify either month's figure. My argument is about what the statistic can support, which holds regardless of the exact number.