The two formulas, as Python expressions

Answer

pct_change = (cur - base) / base common_size = line / revenue

Horizontal: change divided by the BASE year (never the current year). Vertical: each line divided by the statement’s own base — revenue on an income statement, total assets on a balance sheet.

Heisinger & Hoyle §13.1–13.2; Lyryx Intro FA §12.7; Bigel §5.4