Most opex is closer to fixed than COGS is, which is the source of operating-leverage. If revenue rises 20% and opex rises 6%, operating profit rises far faster than 20%. The same maths works brutally in reverse.
Example: Northwind Tools spends $250M of opex: $160M of SG&A and $90M of R&D. On $370M of gross profit that leaves $120M of operating income. A 10% opex cut with flat revenue would lift operating income by 21%.
Original diagrams for the ideas on this page. Illustrative, not real market data.
Margin and leverage. A $5,000 deposit can control a $100,000 position, which is 20:1 leverage. Because the loss is measured on the full $100,000, a 2.5% move against you halves the deposit and brings a margin call, and a 5% move uses all of it.
Educational only, not advice. Spotted an error? Post in Site Feedback.