A public inbox for challenges is being set up. Until then, the source link and CSV on every chart let you check any figure yourself.
Axis, calculation and broken-citation reports don’t need a competing dataset. If you do bring one, include the published dataset name, the time window, the geography, the units and any transformation.
Accepted challenges are published on corrections with the old figure, the new figure and the reason. A disagreement that is not adopted stays private.
Error in the figure
The number shown doesn’t match the source file.
Axis or scale
The chart misleads by its range, baseline or labels.
Calculation
A derived series (ratio, change, real dollars) is computed wrong.
Broken citation
A source link or vintage is dead or wrong.
Counter-dataset
A better published series answers the same question.