The definition
Of all brand-naming events across your prompt corpus, in a given window, on a given engine set, what share belongs to you? That is Recommendation Share. It is deliberately relative — it moves when competitors move, which is the point.
Defining the competitive set
Include too few competitors and the metric flatters you. Include everything the engines ever name and it becomes noise. The workable rule is to include every brand the engines name above a frequency floor across the corpus, whether or not you consider them a competitor — the engine's opinion is the one being measured.
Weighting
Ranked events carry the most weight, cited next, mentioned least. Weights are fixed and published so scores remain comparable across windows; tuning weights to make a number look better destroys the series.
Confidence and honest reporting
Because sampling is repeated and engines are stochastic, every reported share carries an interval. A two-point move inside a five-point interval is not a result. Report the interval alongside the number, always.
