W.E.T. Midterm Control Index: methodology

The W.E.T. Midterm Control Index is a daily 0–100 reading of how contested the 2026 US midterm map is.

Components

Active midterm markets — House and Senate control, individual seat races, governorships — resolving on the midterm calendar. Each race contributes once, through its leading market.

Value

The volume-weighted mean competitiveness 1 − 2|p − 0.5| across races, 0–100. A map of coin-flips reads near 100; a map of safe seats reads near 0. No single market may exceed its weight cap (excess redistributed), so one whale contract can't be the index. Each real-world event contributes once, through its leading qualifying market. When too few qualifying markets are live, the index reports insufficient data rather than a number.

Publication & freshness

Computed and published daily to a durable, dated snapshot; the "last moved" date advances only on a real move, drivers attribute each daily change to the markets that caused it, and every point is appended to a permanent, citable history.

What this index is not

This is a benchmark reading of market prices, not a W.E.T. forecast and not advice. A high value does not predict that the event happens — it reports what prediction-market traders are collectively pricing right now. Prices move continuously and can be wrong.

An accuracy record for a benchmark requires resolved outcomes accumulated over time. W.E.T. publishes this index daily with a dated, immutable history from first publication — that published series is the audit trail. Calibration analysis will ship strictly when the resolved-outcome corpus supports it, never before. See the site methodology for the same discipline applied to the W.E.T. Score.