v3.25.2
STOCK-BASED COMPENSATION (Tables)
 6 Months Ended
Jun. 30, 2025
Share-Based Payment Arrangement [Abstract]  
Stock-based compensation expense Stock-based compensation expense was as follows:
 Three Months Ended June 30,Six Months Ended June 30,
 2025202420252024
Stock Compensation Expense($ in millions)
Stock-based compensation$9.2 $5.4 $14.5 $11.0 
Mark-to-market adjustments(1.9)(5.4)(5.7)(3.2)
Total expense$7.3 $— $8.8 $7.8 
Schedule of fair value of performance share awards granted valuation assumptions The fair value of each performance share award based on TSR was estimated on the date of grant, using a Monte Carlo simulation model with the following weighted average assumptions:
Grant Date Assumptions - Performance Shares20252024
Risk-free interest rate4.27 %4.53 %
Expected volatility of Olin common stock37 %41 %
Expected average volatility of peer companies35 %37 %
Average correlation coefficient of peer companies0.450.40
Expected life (years)3.03.0
Grant date fair value (TSR-based award)$27.46$72.80
Grant date fair value (net income-based award)$27.62$54.07
Performance share awards granted573,479180,714