Note 12. Stock Compensation
We recorded $249.3 million, $266.1 million and $215.9 million, respectively, of stock compensation expense for the years ended December 31, 2025, 2024 and 2023. Stock compensation expense within the consolidated statements of operations included research and development expense for the years ended December 31, 2025, 2024 and 2023 of $150.2 million, $161.3 million and $126.7 million, respectively. Stock compensation expense within the consolidated statements of operations also included selling, general and administrative expense for the years ended December 31, 2025, 2024 and 2023 of $95.6 million, $102.5 million and $86.1 million, respectively. Stock compensation expense within the consolidated statements of operations also included cost of product revenues for the years ended December 31, 2025, 2024 and 2023 of $3.5 million, $2.3 million and $3.1 million, respectively.
Additionally, as described in Note 5, as part of the Escient acquisition, during the year ended December 31, 2024, we recognized on our consolidated statements of operations related compensation expense of approximately $31.5 million associated with the accelerated vesting for certain Escient stock awards in connection with the acquisition.
We utilized the Black-Scholes valuation model for estimating the fair value of the stock options granted, with the following weighted-average assumptions:
Employee Stock Options
For the year ended December 31,
Employee Stock Purchase Plan
For the year ended December 31,
202520242023202520242023
Average risk-free interest rates4.10 %4.15 %4.01 %3.95 %4.88 %4.72 %
Average expected life (in years)5.025.035.050.500.500.50
Volatility29 %30 %32 %34 %27 %25 %
Weighted-average fair value (in dollars)24.0021.0724.3515.9012.3412.68
The risk-free interest rate is derived from the U.S. Federal Reserve rate in effect at the time of grant. The expected life calculation is based on the observed and expected time to the exercise of options by our employees based on historical exercise patterns for similar type options. Expected volatility is based on the historical volatility of our common stock over the period commensurate with the expected life of the options. A dividend yield of zero is assumed based on the fact that we have never paid cash dividends and have no present intention to pay cash dividends. Nonemployee awards are measured on the grant date by estimating the fair value of the equity instruments to be issued using the expected term, similar to our employee awards.
We estimate forfeiture rates for our options, RSUs and PSUs. Under the true-up provisions of the stock compensation guidance, we will record additional expense as the awards vest if the actual forfeiture rate is lower than we estimated, and will record a recovery of prior expense if the actual forfeiture is higher than we estimated.
Total compensation cost of options granted but not yet vested as of December 31, 2025, was $21.8 million, which is expected to be recognized over the weighted average period of 1.3 years. Total compensation cost of RSUs granted but not yet vested, as of December 31, 2025, was $248.9 million, which is expected to be recognized over the weighted average period of 1.5 years. Total compensation cost of PSUs granted but not yet vested, as of December 31, 2025, was $40.2 million, which is expected to be recognized over the weighted average period of 2.3 years, should the underlying performance conditions be deemed probable of achievement.

Historical Timeline

Fiscal YearFiled
2025Feb 10, 2026Showing above
2024Feb 10, 2025
2023Feb 13, 2024
2022Feb 7, 2023
2021Feb 8, 2022
2020Feb 9, 2021
2019Feb 13, 2020
2018Feb 14, 2019
2017Feb 15, 2018
2016Feb 14, 2017
2015Feb 12, 2016

About Stock Compensation Disclosures

Stock-based compensation disclosures detail the equity awards granted to employees and executives — including stock options, restricted stock units (RSUs), and performance shares — along with the valuation methods and assumptions used to expense them. This section reveals the true cost of talent retention and the alignment between management incentives and shareholder interests.

Key signals: total unrecognized compensation expense and its expected recognition period signal future earnings headwinds from already-granted awards. For stock options, examine Black-Scholes assumptions — expected volatility, risk-free rate, and expected term — as understating any of these reduces reported compensation expense. Compare stock compensation expense as a percentage of revenue against peers to assess dilution cost. Watch vesting schedules for acceleration clauses tied to change-of-control events. Performance-based awards with undemanding targets may indicate weak governance. Add back stock compensation to operating cash flow to calculate a more conservative free cash flow figure.