How does early-exercise behavior affect the expected-term adjustment for employee options?

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AcadiFi · Accepted Answer

Early exercise by employees reduces option value because it forfeits remaining time value. Expected term captures this: if the contractual term is 10 years but employees typically exercise at year 5, use T=5. Three methods for estimating expected term: 1. SIMPLIFIED METHOD (SEC SAB 107/110): Expected term = (vesting period + contractual term)/2. Only permitted for 'plain vanilla' options from companies lacking exercise history. For a 4-year cliff vest, 10-year option: (4+10)/2 = 7 years. 2. HISTORICAL METHOD: Compute time-weighted average of actual past exercises, forfeitures, and outstanding options. Requires robust exercise database. If historical shows median exercise at year 5.5, use 5.5. 3. LATTICE-IMPLIED METHOD: Build a lattice with an exercise boundary (e.g., exercise when S >= 2K). The average exercise time across paths becomes the expected term implied by the lattice. Feed this back into Black-Scholes. Worked example: Ravenna Industrial has 8 years of exercise data showing employees exercise at mean time 5.8 years with 12% forfeiture rate before vest. Rather than using simplified 7.0, they use 5.8. For a $45 strike at $45 spot with vol 42%, rf 4.1%, div 1.2%: - T=7: Black-Scholes ≈ $18.90 - T=5.8: Black-Scholes ≈ $16.80 The 1.2-year reduction saves $2.10 per option × 200,000 options = $420,000 in total grant-date fair value, spread over vesting. ```mermaid flowchart LR A[Contractual 10yr] --> B[Employee
behavior] B --> C[Expected Term
5-7yr] C --> D[Reduced FV] ``` Analytical note: shorter expected term lowers SBC expense — management has incentive to justify shorter terms.

How does early-exercise behavior affect the expected-term adjustment for employee options?

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