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Methodology

TDB Composite Index (TCI)

The TDB Composite Index is a proprietary, dimensionless price index that transforms raw multi-source commodity price data into relative movements. Each product is indexed to a base value at its earliest observation date. No absolute prices are exposed, making the index safe for external publication.

Data Sources

The TCI aggregates price data from multiple independent sources, each weighted according to its reliability, coverage, and update frequency. The exact weighting methodology is proprietary.

Source Type Coverage Status
SunSirs Commodity Prices Multi-sector commodity coverage Active
EIA Energy Prices US Petroleum and energy markets Active
FRED Economic Indicators Producer Price Indices for chemicals Active
GTA Trade Policy Global trade policy interventions Policy
Federal Register Trade Policy US tariffs, antidumping, countervailing duties Policy

Trade policy sources (GTA, Federal Register) do not contribute to the TCI price index. They provide a separate intelligence layer for supply chain risk assessment.

Calculation Method

  1. Per-source normalization. Each source is independently normalized to a common base value, making sources with different absolute price levels comparable.
  2. Weighted composite. The TCI is computed as a proprietary weighted average of all available normalized source values. Missing observations are handled through forward-fill interpolation.
  3. Percentage deltas. Change metrics are computed across multiple time horizons: Week-over-Week (WoW), Month-over-Month (MoM), and Quarter-over-Quarter (QoQ).
  4. Source spread. Measures divergence between data providers. A high spread indicates disagreement across sources.
  5. Volatility. Short-term rolling standard deviation of daily percentage changes in the composite index.
  6. Trend classification. Compares short-term and long-term moving averages using a threshold-based classification into RISING, STABLE, or FALLING.

Confidence Scoring

Each product receives a confidence rating based on the number of independent sources contributing data on its most recent observation date:

HIGH ███ 3 or more contributing sources MEDIUM ██░ 2 contributing sources LOW █░░ 1 contributing source

Confidence reflects data coverage, not accuracy. A LOW rating means the product is currently tracked by a single source. The majority of products fall into this category as source overlap across chemical commodities remains limited.

Update Frequency

The index is updated automatically every day. A scheduled pipeline collects data from all active sources, recalculates the TCI for every product, and deploys updated figures to the website without manual intervention.

As of February 2026, the index covers 413 products across 485 tracked price series.

Limitations