Allocating Value Across a Cap Table: OPM and PWERM

A startup raises venture funding, and the preferred shares that investors bought come with a liquidation preference: if the company is sold, preferred holders get their money back (or more) before common shareholders — founders and employees — see a cent. That single contractual term means a share of preferred stock and a share of common stock in the exact same company are not worth the same amount, even though both are "equity" — and a 409A valuation has to split the company's total equity value between them correctly, or employee stock options get priced wrong.

Two ways to split the same pie

The option pricing model (OPM) treats the total equity value of the company as a single pie, and treats each class of shares — the liquidation preference, the common — as a call option with a different "strike price" corresponding to where that layer sits in the payout order. Common stock, for instance, behaves like a call option struck at the total liquidation preference: it's worth nothing until enough value accrues to pay off everyone ahead of it, then participates in everything above that. This is done using an options-pricing formula (typically Black-Scholes-style), so it needs an assumed volatility and time to a liquidity event, but doesn't require enumerating specific exit scenarios.

The probability-weighted expected return method (PWERM) instead lays out a handful of explicit future scenarios — an IPO at a high valuation, an acquisition at a moderate valuation, a modest sale, dissolution — assigns a probability and payout to each share class under each scenario, and weights them together. It requires more judgment about which scenarios and probabilities are realistic, but is more intuitive and transparent than the option-based math of OPM, and works well when a specific near-term outcome (like an already-negotiated acquisition) is likely.

Worked example (simplified PWERM)

A company has $5 million of preferred liquidation preference outstanding and 10 million total shares, 4 million of them preferred and 6 million common. Three exit scenarios are modeled:

1. Low exit, $3 million, 40% probability. Preferred takes the full $3 million (below their $5 million preference); common gets $0.
2. Mid exit, $20 million, 40% probability. Preferred takes their $5 million preference; remaining $15 million split pro-rata across all 10 million shares as if converted, so common's 6 million shares get 15\text{m} \times 0.6 = \9 million, or \1.50/share.
3. High exit, $60 million, 20% probability. Same structure: preferred takes $5 million, remaining $55 million split pro-rata, common gets 55\text{m} \times 0.6 = \33 million, or \5.50/share.

Probability-weighted common share value: (0 \times 0.40) + (1.50 \times 0.40) + (5.50 \times 0.20) = 0 + 0.60 + 1.10 = \1.70$ per common share.

What this means in practice

This allocation directly sets the strike price used for employee stock options in a 409A valuation — price common stock too high and options become unattractive compensation; price it too low (or fail to defend the methodology) and the company risks a tax penalty for underpricing compensation. OPM is more common for early-stage companies with no clear near-term exit path, while PWERM is preferred once a specific transaction or IPO timeline is reasonably visible.