Index methodology

All Tantalum Strategy indexes are calculated from publicly sourced inputs and published on a weekly cadence (Friday close, posted Monday morning UTC). Constituent materials and the thesis behind each index are open. Exact weights, proxies for materials without spot markets, and the calculation kernel are the editorial judgment of the desk.

The three indexes at a glance

TAI · Tantalum AI Materials Index. Tracks the physical inputs whose supply must scale or AI infrastructure breaks. A composite of two sub-indices: TAI-M (materials) and TAI-P (power), weighted 75/25.

SOV50 · Sovereignty 50. A risk indicator, not a return index. Quantifies supply-concentration exposure: if a single dominant producing country closed the spigot tomorrow, how much AI-relevant supply would be at risk?

SDX · Southern Diversification Index. A thesis index pairing with SOV50. Tracks the alternative supply base for AI-relevant materials outside the China + DRC nexus: Brazil, the Lithium Triangle, the African Copperbelt, plus selective Australian and Angolan producers.

TAI as a composite

TAI was originally a single basket. Combining materials and power inputs in one basket creates a signal-to-noise problem: a TAI move could come from a rare-earth supply tightening or from a hurricane spike in natural gas, and the headline number doesn't tell you which. In May 2026 we split TAI into two openly published sub-indices:

• TAI-M (AI Materials): pure mineral exposure. Copper, rare earth basket, niobium, gallium, germanium, helium, lithium. Power deliberately excluded.
• TAI-P (AI Power): electricity inputs for AI infrastructure. Uranium and nuclear utility equity (the leading-edge story: hyperscaler PPAs with Constellation, Talen, Oklo, NuScale), broad utility sector equity, natural gas as a residual proxy.

Top-line TAI = 75% TAI-M + 25% TAI-P. Both sub-indices are published and updated independently. Readers can decompose any TAI move into its materials and power contributions.

Data sources

Input prices are sourced from publicly available endpoints: COMEX and NYMEX futures via Stooq.com (delayed market close), ETF proxies (REMX for rare earth, LIT for lithium, URA for uranium, NLR for nuclear utilities, XLU for the broad utility sector, SOXX for semiconductor demand as a Ga/Ge proxy, VALE and FCX for Brazilian and DRC mining equity exposure) for materials without transparent spot markets, USGS quarterly reference prices for gallium, germanium, and helium, and EIA / Henry Hub for the natural gas component.

We do not use paid commodity-price feeds. All inputs are reproducible from public data so any reader can re-derive the headline number from the open inputs and the methodology described here.

Editorial overlay

Each published index value is the output of two layers: a weighted base computation (constituent price ratios × weights) and an editorial overlay applied at publication time. The base is open and reproducible from the constituent list. The overlay is proprietary.

The overlay scope is documented openly. It incorporates a desk review of three signal categories: (1) geopolitical flow — export-control announcements, sanctions, country-specific supply disruptions, (2) supply-chain news triage — major contract signings, project starts/stops, refinery commissioning, (3) technical-momentum filtering — smoothing transient moves and weighting longer-horizon trend confirmation. The exact kernel that combines these into a per-index adjustment, and the magnitude bounds applied, are editorial judgment of the desk.

This is intentional, not theatrical. Naive replication of the indexes from public commodity feeds alone will diverge from the published values within weeks because the overlay corrects for noise, applies editorial judgment on signal weight, and embeds desk-level context that pure price math cannot capture. Institutional licensing includes the kernel under separate agreement.

Multi-model adversarial validation

Editorial output passes through a structured adversarial review across independent frontier models before publication. One model drafts. A separate model independently re-verifies every numerical claim and every cited source against the underlying public references. Only output that survives both passes ships. Disagreement between the two passes is treated as a signal in itself: it either surfaces a fact that needs to be revised, a citation that needs to be dropped, or an editorial framing that overreaches what the sources actually support.

This applies to research articles and to the per-index editorial overlay alike. The desk publishes the framework openly because it is part of what readers are buying when they read Tantalum. The exact models, the verification prompt structure, and the disagreement-resolution kernel are not published — that's where the operational moat lives, not in the constituents or the cadence.

The point is not that this prevents every error. It tightens the loop between drafting and publication so that fabricated specifics (made-up citations, drifted dates, plausible-but-uncited numbers) get caught at the gate rather than in the wild. The desk treats reader trust as the load-bearing asset of the entire product.

Watermark and provenance

Each published index value contains a deterministic micro-adjustment of approximately ±0.05 derived from a secret seed and the publication date. This is invisible to readers and does not affect any directional or magnitude read of the index. It exists so that if a competitor or third-party were to publish an index suspiciously close to ours, we can verify whether the values originated from our publication by checking the watermark pattern. Standard provenance practice for proprietary data products.

What we publish, what we don't

Public: the constituent materials of each index, the source we use to track each one, the broad thesis behind every cut, the update cadence, and the data providers we read.

Proprietary: the exact weight of each constituent, the precise price proxy used for materials without a clean spot market (e.g., what we use as a niobium proxy when CBMM trades privately, or how we blend USGS quarterly reference prices into a weekly mark), and the calculation kernel. These are the desk's editorial judgment and are revised over time as the AI-materials thesis evolves.

Institutional clients can license the full methodology, constituents, weights, and historical data under separate agreement. Talk to the desk →

Update cadence

Each sub-index and headline value is recalculated weekly, on Friday after US market close, and published Monday morning UTC. A scheduled job fetches the latest commodity and ETF closes on weekdays at 22:15 UTC, recomputes the indexes, and commits the new data to the site repo. Vercel auto-deploys the refreshed numbers within ~60 seconds of that commit.

Daily ticker values on the home page reflect the most recent close. The ticker label shows the date of the underlying data so readers can see when it was last refreshed.

Limitations (read this)

Honesty is the editorial position of the desk, including about our own indexes. Three limitations a serious reader should know about:

1. No backtest validation yet. The indexes started publishing in early 2026. Until at least a year of live data has been recorded and a backtest against synthetic constituents can be run, treat the YTD numbers as directional, not validated. We plan to publish a backtest review on the one-year anniversary.
2. Thin-market proxies are imperfect. Gallium, germanium, helium, and niobium do not have transparent daily spot markets. We use a combination of USGS quarterly reference prices and equity proxies (SOXX for semiconductor demand, VALE for Brazilian mining cluster) to track them on a weekly cadence. These proxies move for reasons other than the underlying material's actual supply-demand balance. We disclose the proxy choices on this page; we revise them as cleaner data becomes available.
3. Editorial weights, not optimized weights. The constituent weights inside each index are the desk's view of what matters for the AI-materials thesis right now. They are not the output of a portfolio-optimization model or a covariance-minimization procedure. As the thesis evolves and as new data sources become available, weights are revised. Major weight changes are noted on this page with the date.

None of this makes the indexes useless. It does mean they are best read as thematic indexes (closer to MVIS, Solactive thematic) rather than as benchmark indexes (S&P GSCI, Bloomberg Commodity). The numbers are directional and editorially honest. They are not yet ready for use as a settlement reference for a derivative or a fund.

The path to more rigor

The roadmap to make these indexes institutionally license-ready:

1. One year of live data. Publish weekly from Jan 2026 forward. Document any methodology changes with dates. Build a track record.
2. Backtest review at the one-year anniversary. Reconstruct each index back to 2020 using historical Stooq + USGS data. Publish the backtest, including draws and disagreements with the constituents we have today. Adjust weights where the backtest reveals signal/noise problems.
3. Engage a commodity index quant for an independent methodology review. Particularly on TAI-M's handling of thin-market materials and SOV50's risk-bucket weighting. Publish the review along with our response.
4. Document inclusion / exclusion criteria. Every constituent needs a written rationale for why it's in. Inspired by MVIS and Solactive's published methodologies.
5. Institutional licensing pilot. Once steps 1–4 are done, offer paid access to full weights and historicals to a small set of institutional readers under separate agreement, with the methodology binding the parties.

Changelog

2026-05-27. Methodology page expanded with a Multi-model adversarial validation section, documenting the editorial review process that runs between drafting and publication.

2026-05-25. TAI restructured from single basket to composite (TAI-M + TAI-P). SOV50 reframed as a risk indicator (not a return index). SOUTH ticker renamed to SDX (Southern Diversification Index) and reframed as a thesis index pairing with SOV50. Methodology page expanded with a Limitations section and a path-to-rigor roadmap.

2026-01-01. All three indexes go live with base value 100.