EPS — Basic vs. Diluted, Dilutive Securities, and Stock-Based Compensation

Basic EPS is straightforward in concept but requires the weighted-average shares outstanding — not just the year-end count. Share counts change during the year from issuances, repurchases, and splits, so you must weight each period's share count by the fraction of the year those shares were outstanding:

• Formula: Basic EPS = Net income available to common shareholders ÷ Weighted-average shares outstanding.
• Net income available to common: this is net income MINUS preferred dividends. Preferred shareholders have a prior claim — their dividends must be subtracted before computing what's 'available' to common shareholders. If net income = $100M and preferred dividends = $10M, the numerator is $90M.
• Weighted-average calculation: Example — a company starts the year with 10M shares, issues 3M more on April 1 (9 months remaining), and repurchases 1M on October 1 (3 months remaining). Weighted-average = (10M × 12/12) + (3M × 9/12) + (−1M × 3/12) = 10M + 2.25M − 0.25M = 12M shares.
• Stock splits retroactively adjust: if a 2-for-1 split occurs in November, all share counts before the split are doubled retroactively for EPS purposes. This ensures EPS is comparable across periods.

Diluted EPS assumes all dilutive securities were converted into common shares at the start of the period, then asks: what would EPS look like in that worst case? GAAP requires reporting both basic and diluted EPS side by side. The treasury stock method is used for stock options and warrants:

• Convertible bonds — if-converted method: assume the bonds are converted to shares at the start of the period. Two adjustments: (1) add the after-tax interest expense back to net income (no longer paid since bonds are converted), and (2) add the new shares to the denominator. Only include if conversion reduces EPS (i.e., dilutive).
• Convertible preferred stock: add back preferred dividends to net income (not paid after conversion) and add conversion shares to denominator. Apply only if dilutive.
• Diluted EPS formula: (Net income + After-tax interest on convertible bonds + Preferred dividends) ÷ (Basic shares + TSM net shares from options + Conversion shares from bonds and preferred).

Stock-based compensation (SBC) is shares or options granted to employees as part of their compensation. It is expensed through the income statement under GAAP (reducing net income) but has a subtle, ongoing dilution effect that is often larger than what investors realize:

• GAAP accounting for SBC: when options are granted, the fair value (typically using Black-Scholes) is estimated. This fair value is expensed over the vesting period. A $60M grant vesting over 3 years = $20M/year in SBC expense on the income statement. This expense reduces GAAP net income — which is why many tech companies show GAAP losses but positive non-GAAP (SBC-excluded) earnings.
• The dilution problem: when options vest and are exercised, new shares are issued — diluting existing shareholders. The income statement captured the expense, but the dilution happens at exercise, not grant. If the stock has risen significantly since grant, the dilution (in shares) is large even though the expense was based on the original fair value.
• Diluted EPS partially captures this: in-the-money outstanding options are included in the diluted share count via the treasury stock method. But unvested options in future periods are not yet included in the current-period diluted EPS calculation.
• Non-GAAP EPS and SBC: many technology companies report 'adjusted EPS' that adds back SBC expense. This produces a higher EPS number — but investors should be wary. SBC is real economic dilution. Excluding it from 'adjusted earnings' while real shares are issued understates the true per-share cost of operations. Buffett famously criticizes stock option accounting as leaving out a real cost. Adding back SBC in adjusted earnings consistently overstates the earnings per share that long-term investors actually receive.