Number 23/Measurement & inference/Monitoring
The Detection Lag
The quantity
The ratio of recorded to actual change in a monitored quantity, and its complement, as a function of monitoring effort and method drift.
01Why it matters
It separates a change in the world from a change in the instrument, which is the confound behind a large share of contested environmental trends.
02Expected value
Substantial where methods changed, negligible where they did not.
03How it would be measured
Compare trends from overlapping methods during transition periods.
04What would refute it
If measured and actual change coincide regardless of effort, the lag is zero.