Private Company Valuation: Illiquidity, Control, and Marketability Discounts

Introduction

Private companies present unique valuation challenges because the standard reference points for public company valuation (stock prices, trading multiples, diluted shares) do not exist. There is no stock price to observe, no daily market assessment of value, and no liquid market where ownership interests can be bought and sold quickly. These differences require specific valuation adjustments that can significantly affect the final number.

Private company valuation is relevant across multiple investment banking contexts: M&A advisory (most middle-market sell-side mandates involve private targets), LBO analysis (PE firms acquire private companies), fairness opinions for private transactions, and tax and estate planning (valuing family business interests for transfer tax purposes).

No Observable Market Price

For public companies, the share price provides a real-time, market-determined valuation. For private companies, there is no such anchor. The value must be estimated entirely from analytical methodologies, making the analyst's assumptions and judgment more consequential.

Limited Financial Disclosure

Public companies file quarterly and annual reports with standardized financial data. Private companies have no such disclosure requirements. Financial data may be limited, unaudited, or prepared under different accounting standards (cash-basis vs. accrual, for example). Normalized EBITDA may require more extensive adjustments for private companies (owner compensation, related-party transactions, personal expenses).

Different Capital Structures

Private companies may have complex capital structures with multiple classes of equity (common, preferred with different liquidation preferences, convertible notes, SAFEs, options) that affect how value is distributed among stakeholders. The waterfall analysis (determining how much each class receives at different exit values) is more complex than for public companies with a single class of common stock.

Private companies are valued using the same three pillars as public companies:

Size Premium (in Private Company Valuation)

An additional return premium added to the cost of equity for smaller companies to reflect the empirical observation that smaller companies generate higher returns (and carry higher risk) than larger companies, even after adjusting for beta. In private company valuation, the size premium is sourced from Kroll/Duff & Phelps annual cost of capital data, which categorizes companies by market capitalization decile. The smallest decile (micro-cap) has historically shown an excess return of 3-5% above CAPM predictions. For a private company with $50 million in revenue being valued against public peers with $5 billion in revenue, adding a 3-4% size premium to the cost of equity can increase WACC by 2-3 percentage points, reducing the DCF-implied value by 15-25%. The size premium is debated (some academics argue it has diminished), but it remains standard practice in formal private company valuations.

Discount for Lack of Marketability (DLOM)

A reduction applied to the value of a private company's equity to reflect the fact that the shares cannot be sold quickly on a public exchange. The discount compensates the holder for the illiquidity: the time, cost, and uncertainty of finding a buyer and completing a sale. DLOM is estimated using restricted stock studies (comparing the price of restricted shares that cannot be traded for a period to freely tradable shares of the same company), pre-IPO studies (comparing private placement prices to subsequent IPO prices), and option pricing models (modeling the cost of illiquidity as the price of a put option that the holder cannot exercise). Typical DLOM ranges are 15-40% for minority interests and 5-15% for controlling interests.

Methods for Estimating DLOM

Restricted stock studies: Compare the price at which companies issued restricted shares (which cannot be publicly traded for a specified period) to the price of the same company's freely tradable shares. The average discount is typically 20-35%, though it varies with the restriction period, company size, and profitability.

Pre-IPO studies: Compare the price at which private placements occurred before an IPO to the actual IPO price. These studies typically show discounts of 40-60%, though they are criticized for conflating marketability effects with company-specific changes between the private placement and the IPO.

Option pricing models: Model the DLOM as the cost of a put option that the holder cannot exercise (because the shares are illiquid). This approach uses the Black-Scholes framework with inputs for volatility, expected holding period, and risk-free rate.

Factors That Affect DLOM Magnitude

The DLOC applies when valuing a minority interest that cannot control corporate decisions (dividend policy, management selection, capital allocation, exit timing). A 10% stake in a private company is worth less per share than a controlling 51% stake because the minority holder has no power to influence how value is created or distributed.

DLOC and control premiums are mathematically related:

If the control premium is 30%, the DLOC is approximately 23%.

When valuing a minority interest in a private company, both DLOM and DLOC may apply, compounding the discounts:

If a company is worth $100 million at a public, control level, and the DLOC is 20% and DLOM is 30%, a minority private interest would be valued at: $100M x 0.80 x 0.70 = $56 million. The combined discount of 44% illustrates why minority interests in private companies trade at dramatic discounts to public company equivalents.