CourseAI / ML Engineer: The Complete Course · Module 5: Data Engineering for ML · part 37 of 93
Part 37 · Module 5: Data Engineering for ML

Incident: A computed input was wrong for three weeks

15 min read·
Module 5 · Incident file · About 35 minutes · Needs: Lesson 3 (data contracts) and Lesson 4 (training-serving skew, online and offline parity); Module 3 lesson 3's warning threshold

What happened

WHAT HAPPENED Three weeks of miscalculated scores some scores miscalculated 17 Mar 2022 issue starts 6 Apr fixed late May first press report 2 Aug 2022 Equifax statement
The issue ran from 17 March to 6 April 2022 (red) and was fixed on 6 April (green); it was first reported in late May (grey) and Equifax's statement followed on 2 August.

On 2 August 2022 Equifax published "Equifax Statement on Recent Coding Issue" (Equifax newsroom, 2 August 2022). It "identified a coding issue within a legacy, on-premise server environment in the U.S. slated to be migrated to the new Equifax Cloud infrastructure". The issue "impacted how some credit scores were calculated".

It ran "between March 17 and April 6" 2022 and was "fixed on April 6". "Information in consumer credit reports was not changed as a result of this issue." Equifax's analysis found "no shift in the majority of scores" and that "less than 300,000 consumers experienced a score shift of 25 points or more", adding that a shift "does not necessarily mean that a consumer's credit decision was negatively impacted".

WHAT HAPPENED Who said what SOURCE CLAIM Equifax under 300,000 shifted 25+ points Equifax credit reports not changed WSJ, via The Register scores off by 20 points or more Unnamed source, via NMP attributes wrong in ~12% of calcs
Equifax's own figures (blue, green) are kept apart from what others reported (grey): the Wall Street Journal's 20-point shifts and an unnamed source's 12% of calculations.

The Register reported the statement the next day (Thomas Claburn, The Register, 3 August 2022), quoting Equifax that the issue "resulted in the potential miscalculation of certain attributes used in model calculations". It adds what others reported, and those claims are theirs, not Equifax's. The Wall Street Journal reported scores provided to lenders "off by 20 points or more". National Mortgage Professional, which first reported it in late May, cited an unnamed source: attribute values such as "number of inquiries within one month" were "sometimes incorrect", in about 12 percent of score calculations. Equifax did not say what the coding issue was; The Register asked and had no reply.

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