Plain definition
A leading indicator is a measure that changes early enough to give warning about a later outcome. It does not predict the future with certainty; its value is that management can still act before the lagging result is final.
Illustrative example
A manufacturer tracks qualified quotations accepted by customers as a leading indicator for next-quarter revenue. In April, accepted quotations fall from 80 to 50 while booked revenue remains on plan because current orders are still being delivered. Sales investigates the drop, finds a slower response time to inbound leads, and assigns an additional estimator. The action may improve later revenue, but only if the link between quotes and orders holds.
A measure is leading only for a specific later outcome and a useful time window. The same measure can be irrelevant for another decision.
Why it matters
If management waits for revenue to fall, it may have lost the time needed to change marketing, pricing, capacity, or customer follow-up. Leading indicators move attention from explaining a finished result to testing an early signal.
Practical consequence
Use operating history to test the relationship, timing, and exceptions between the early measure and the later result. Define the population and data source, set a review threshold, and name the action to consider when it moves. Keep a lagging outcome alongside it to confirm whether the signal is working; an attractive early metric without this check can create false confidence.