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Each index listed measures the rate of change of that company’s secondary market composite midpoint relative to its own recent history. Primi trades momentum and trajectory, not absolute valuation or share price.

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Why not track price directly?

For large, successful private companies, the direction is not in question. Everyone knows companies like Anthropic, OpenAI, and SpaceX are worth more today than two years ago and will likely be worth more two years from now. Trading that is a one-sided market and would not be meaningful.

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Why not track momentum alone?

A pure momentum index partially addresses this but still has an upward bias for companies in sustained high-growth phases. If a company has been appreciating consistently, even a momentum index reflecting that rate keeps rising. The genuinely uncertain question is not where a company is valued, but whether it is appreciating faster or slower than its own history.

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Excess momentum over a baseline

Primi measures the excess of current 60-day momentum over each company’s own trailing 12-month average rate of change. This is the signal.
  • When current momentum exceeds the baseline, the index rises.
  • When it falls below the baseline, the index falls.
  • When current momentum exactly matches the baseline, the index stays flat — regardless of whether the absolute price is still rising.
A company can have an excellent quarter and still see its Primi index fall if the market expected an even better quarter based on recent history. This is precisely how equity markets create two-sided trading for excellent companies: the price reflects performance relative to expectations, not performance in absolute terms.

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Precedents

This approach has established precedents. The VIX is the closest structural analogy — CBOE calculates it from raw bid-ask quotes across independent exchanges, and a separate exchange trades futures on top of it. The MSCI Momentum Index applies the same excess-over-baseline logic to public equities. Coinbase Derivatives received CFTC approval for perpetual futures referencing independent spot markets. Primi applies these same established structures to private company secondary markets. Momentum as a tradable signal is one of the most documented return factors in finance, validated across asset classes for decades. Applied here, it solves the directional bias problem.

The Formula

Step-by-step index calculation.

Data

Source platforms, collection, and filters.