Economists

An economic indicator that worked well as a passive measure often degrades the moment policy or incentives start targeting it directly — the measure and the reality it tracked quietly come apart.

An instrumental variable doesn't need to be interesting on its own — it just needs to move the variable you care about, without having any other plausible path to affecting the outcome you're studying.

Instrumental variables analysis only works as well as its instrument's actual strength — a weak instrument can produce an estimate less trustworthy than the simpler, more direct regression it was meant to improve upon.

A single elasticity number presented without its estimation conditions is not a fact about your product — it's a fact about the specific price range and time window it was measured in.