Outline — WTI Went Negative. Brent Didn't.

The skeleton. Prose is a rendering of this; if the prose drifts from the argument here, the prose is wrong. See #10.

Story #3, written the #10 way: outline and chart plan committed before any prose. Draws on oil-prices, enriched in the previous session — the negative-price observation and the "it disappears once averaged" point both came out of SUMMARY.md's "What stands out".

The argument, in one sentence

On 20 April 2020 EIA's WTI Cushing spot price was -$36.98 a barrel** — the only negative value in 25,415 Brent and WTI observations going back to 1986 — while Brent that day was **$17.36, and even one level of averaging erases the negative print.

What this story is about

Both of the two main crude benchmarks fell hard in April 2020; only WTI went below zero, and only for one day. The story shows that the two numbers diverged and how narrow the event was in the data. It does not claim to show why from this dataset: the mechanism (futures expiry, Cushing storage) is outside context, attributed to EIA and the CFTC and stated as their explanation. Not a story about oil-price history in general, and not about the wrangling; that gets one short paragraph at the end.

Argument, in order

1. The chart, first. Brent and WTI daily spot prices, March–May 2020. WTI dips below the zero line on 20 April; Brent, plotted alongside, does not. Show this before any prose beyond a one-line caption.
2. What these numbers are. Both series are EIA's daily "spot price FOB" in nominal US dollars per barrel: Brent (series RBRTE) for North Sea crude, WTI (series RWTC) for crude at Cushing, Oklahoma — a landlocked pipeline and storage hub. These are two different crude grades at two different locations, not one commodity priced twice. Caveat, stated plainly: these are spot prices, not futures. The widely reported -$37.63** is the NYMEX May 2020 futures *settlement* on 20 April ([CFTC interim staff report, Nov 2020](https://www.cftc.gov/PressRoom/PressReleases/8315-20)); EIA's spot figure for the same day is **-$36.98. Related, not the same number — the prose must not swap them.
3. What it says.
   • WTI: $18.31** (Fri 17 Apr) → **-$36.98 (Mon 20 Apr) → $8.91** (Tue 21 Apr). Down **$55.29 in one trading day (the 18th and 19th were a weekend), up $45.89 the next.
   • Brent, the same days: $19.75** → **$17.36 → $9.12. Brent's $9.12 on 21 Apr is 2 cents above its all-time daily low of **$9.10** (10 Dec 1998, across the full 1987–2026 record), and within 21 cents of WTI that day. So "Brent didn't" is narrow: both fell hard; only WTI went negative, and only on 20 April.
   • The dip barely survives even one level of averaging. WTI's weekly average for the week ending Fri 24 Apr (the mean of the five daily prices, including -$36.98) is **$3.32** — positive, and the lowest value in any of the six averaged series. Monthly (April 2020, dated to the 15th): $16.55 — not even WTI's lowest month (that is $11.35, Dec 1998). The 2020 annual average (dated 30 June): **$39.16**.
   • Of the 25,415 daily/weekly/monthly/annual observations across all eight series in this dataset, exactly one is negative.
4. Outside context: the explanation others give. One or two sentences, attributed, not presented as something this data shows. EIA's account (Today in Energy, 27 Apr 2020): the May WTI futures contract expired on 21 April; holders who could not take physical delivery could not find buyers, and with Cushing storage scarce (76% full on 17 April, with some of the rest already committed) some paid counterparties to take their contracts. The spot price for Cushing delivery fell with it. Caveat: this dataset contains prices only — it cannot test why WTI went negative, nor why Brent did not; the prose says so rather than supplying a mechanism for Brent. Nominal-dollars caveat: every figure here, including the 1998 comparison, is nominal USD as EIA published it — not adjusted for inflation.
5. How this was made. Brief. Both series come from oil-prices in this repo — EIA's own .xls workbooks, rebuilt by build.ts; the consolidated statistics table that surfaced the "exactly one negative value" claim is enrich.ts's work, local to this repo (not part of any published dataset). The community datasets/oil-prices package is the same underlying EIA source, independently re-wrangled; see the structure benchmark for the row-for-row comparison.
6. Friction notes (keep — for the skill work):
   • The story's argument is a comparison between two resources at one moment (like story #2's scoreboard), not a single time series (like story #1) — but unlike story #2 it still resolves to a plain line chart, because both resources share units and a time axis. The "multi-resource but still a line chart" case wasn't covered by either existing outline.
   • enrich's consolidated stats table (this session's other task, datapressr-q96) is what actually surfaced this finding — scanning the min column across all eight rows is what turned up the single negative cell. Without a table that put every resource's min in one place, this argument would have needed a manual per-file scan to find. Worth noting in enrich's skill draft as a reason the consolidated table earns its keep, beyond tidiness.
   • The "spot vs futures" caveat in beat 2 is deliberately short, not a derivatives explainer — matching the voice guide's "one clear caveat > three confident claims." A longer treatment would turn this into an article about futures markets, which is not the argument.
   • Outline review (datapressr-0cp, round 1) caught the first draft explaining why from a price-only dataset, a mis-stated "round trip in one trading day", and omitting Brent's $9.12 the next day — the omission made the headline contrast look stronger than the data supports. Worth a line in the story skill: the outline must list the numbers that weaken the argument, not only the ones that make it.

Chart plan

Both rendered by oil-prices-make-charts.mjs with Observable Plot per docs/charting.md — annotate directly on the charts rather than relying on a legend.

Voice

Plain and factual, per docs/voice-guide.md. Let the two numbers on the same day — $17.36 and -$36.98 — carry the contrast, and let Brent's $9.12 the next day keep it honest. No "unprecedented", no "the day the market broke". The futures/storage explanation is attributed outside context, not a lecture and not a claim this data proves. A "sounds like me" pass is a separate step the author runs.