No. 292 · Evidence · Systems
Proxy
A stand-in measure is only useful while it moves in step with what really matters.
In the Almanac
“Canaries in the coal mine”, 1890s–1986 · “Optum”, 2019
Both stories in full, three ways to use it and where it misleads.
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Questions
What is Proxy?
A proxy is what we measure when the real target is hard to see: canaries for carbon monoxide, grades for learning, spending for health need. Proxies work only while they move in step with the real thing. A 2019 study found a health algorithm using cost as a proxy for need under-flagged Black patients.
How do you use Proxy?
To use it, name the real goal behind each metric, combine several measures, and check now and then that your stand-ins still track reality.
When does Proxy matter?
Proxy is one of the 68 mental models for evidence, the situations where you ask: Is this really true? Within that, it belongs to “Where information comes from”, alongside Bias from Incentives, Echo Chambers and Filter Bubble.
What is an example of Proxy?
Two stories show it at work: Canaries in the coal mine (1890s–1986) and Optum (2019). Both are told in full in The Mental Models Daily Almanac, which has two stories for each of its 365 models.
Which mental models are related to Proxy?
Goodhart’s Law, Perverse Incentives and The Map is not the Territory. Proxy itself comes from systems.