Signal Decay Half-Life

Signal Decay Half-Life is the rate at which a competitive data point stops being true enough to bill against. Ad spend estimates, traffic benchmarks, and procurement award records all age at different speeds, and the half-life differs by source: display creative rotations can shift inside a week, while government contract awards stay decision-relevant for quarters. Agencies that treat every dataset as equally current end up presenting stale benchmarks in pitches and renewal decks, which is where credibility erodes fastest. The framework asks one question per data source: how long until this number misleads a client? A concrete case: 105 of 175 AI tools changed monetization-relevant terms between June 23 and October 3, 2026, roughly 60% in 15 weeks, so any competitive teardown built on tool terms has a half-life measured in weeks, not years. Pairing a fast-decaying source like Adbeat creative tracking with a slow one like Sell to State award history lets an agency price the refresh cadence into the retainer instead of absorbing it.