Claude
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The source-request loop paid for itself immediately — two of the five corrected something rather than confirming it. The Economist piece settles V1, the riskiest live claim, but our note had over-claimed: truncating the scale is its *first* example, not one of "several." Note rewritten to quote her. The same article turned out to contain a dual-axis chart she caught herself on, now cited. Datawrapper's color-scale part 1 refuted the assumption behind a queued sin outright: it makes no argument against rainbow scales and endorses multi-hue sequential gradients. The rainbow entry is now marked as having no verified source at all, rather than ample backing. The dual-axis post independently draws the same line we drew last turn — of four uses only the alternative-scale case survives, their example being F against C — and led to two references worth more than the blog post: the Isenberg et al. study that tested dual-scale charts, and Few's article working through the cases. Both ship without full metadata rather than guessed metadata; queued. Pie and stacked posts gave verbatim support, plus one correction: a 100%-stacked chart has two readable baselines, not one. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01ULE5RRxdQE1ebwefEd2eCM
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Datawrapper — "Why not to use two axes, and what to use instead"
Lisa Charlotte Muth, blog.datawrapper.de/dualaxis/, published 8 May 2018,
intro updated July 2026. Supplied as PDF, read 2026-08-05.
Answers queue rows 2 and (partly) 1.
The July 2026 revision, verbatim
We originally published this article in May 2018 to explain why you couldn't create dual-axis charts in Datawrapper. Since then, we've changed our minds. We've learned that in some cases, dual-axis charts really are the best way to show the data — and that people who've learned to read them correctly (in financial services, for example) aren't misled by them. […] But all the issues this original article pointed out are still valid. A general audience is indeed likely to misread dual-axis charts.
So: audience-dependent, not a reversal. They now ship the feature on a Business plan and kept the article standing. They also link a newer piece, "What to consider when creating dual-axis charts" (23 July 2026), not supplied here.
They draw the same line we drew
The article lists four reasons people reach for dual axes, then says:
of these four use cases, we think that only the last dual axis chart can be used without being potentially misleading, since it only uses the second Y-axis to show an alternative scale and not a second data series.
The fourth case is Fahrenheit and Celsius on one series — the same example our sin page arrived at independently. Their test and ours match: the sin is a second data series, not a second scale.
The three problems
- "Zero baselines at different heights can mislead." The proportions are arbitrary. Their worked example: German vs global GDP looks like it rises at the same rate; extended to zero, global rose 80% and Germany 40%.
- "Even zero baselines at the same height can mislead" — "humans have a tendency to set things in relation if they're close-by." Readers conclude German GDP exceeded global GDP, then crossed in 2011.
- "They're just hard to read."
Nutshell line: "The scales of dual axis charts are arbitrary and can therefore (deliberately) mislead readers about the relationship between the two data series."
The empirical source behind it — worth citing directly
Isenberg, Bezerianos, Dragicevic & Fekete (2011), A Study on Dual-Scale Data Charts. 15 participants, four chart types; the dual-axis ("superimposed") chart was quoted as:
We found across the board that the superimposed chart performed poorly both in terms of accuracy and time. […] it was ranked lowest by all but one participant. Participants called it very confusing and demanding too much concentration or reflection to decipher the non-monotonic and discontinuous nature of the two scales.
Added to the reference list as isenberg2011. Venue/DOI still needed — queued.
Also flagged: Stephen Few, Dual-Scaled Axes in Graphs: Are They Ever the Best
Solution?, which per Datawrapper concludes he "cannot think of a situation that
warrants them in light of other, better solutions." Added as fewdualaxes;
year and URL queued.
Alternatives they give
Side-by-side charts; indexed charts (with Knaflic's caveat that this fails when one series moves +10000% and the other +5%); prioritise-and-label; connected scatterplot. Our page's repentance already recommends the first two.