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Every year, the HILDA Survey asks

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thousands of Australians about their lives.

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Some questions, they answer alone.

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One is about drugs.

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For decades, economists have asked

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whether drug use costs people at work.

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But people who use drugs differ in other ways.

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Some don't say. And only workers have wages.

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Every household also meets an interviewer.

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They don't ask about drugs.

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Yet what people report

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shifts with who the interviewer was.

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Survey researchers call that error.

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This study uses it.

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Within an area and year,

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who gets which interviewer

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comes down to fieldwork rosters.

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If that's as good as random,

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and interviewers affect pay only through reporting,

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the trace becomes a lever:

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a second way to ask the same question.

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For cannabis, both ways agree:

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about four percent lower hourly pay.

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For frequent methamphetamine use, they split:

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slightly higher pay, if anything, one way;

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almost ten percent lower the other.

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Corrected for testing six drugs,

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it narrowly misses the usual bar:

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a lead, not a verdict.

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For frequent inhalant use,

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the estimated penalty roughly doubles.

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Six drugs. No single answer.

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Some findings hold either way.

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Others depend on where the evidence comes from.

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The noise was never just noise.