Core Definition
Ceteris paribus (Latin): “With other conditions remaining the same.”
The assumption that all variables except the one being studied are held constant. This isolates the effect of a single variable so its relationship to the outcome can be analyzed cleanly.
Cross-Domain Pattern
Beyond the Textbook
Ceteris paribus is not just an economics phrase — it is a universal analysis tool. The same logic appears wherever you need to isolate why something changed.
| Domain | How ceteris paribus appears |
|---|---|
| Economics (demand/supply) | Hold income, preferences, other prices constant to isolate price → quantity relationship |
| FMGT cost analysis | Differential/relevant costs — hold constant what doesn’t change between alternatives to isolate the decision-relevant costs |
| FMGT budgeting | Flexible budget — hold budgeted rates/prices constant, change only volume, to isolate the volume effect vs. the efficiency/price effect |
| FMGT variance analysis | Standard cost variances — hold price at standard to isolate the quantity effect (quantity variance), hold quantity at actual to isolate the price effect (price variance). The multiplier is always the OTHER variable held constant. Responsibility accounting is the WHY: isolate what each manager controls |
| Scientific method | Controlled experiments — change one independent variable, hold all others constant |
Key Insight
The Flexible Budget Connection
Ceteris paribus is not just an economics phrase — it’s a universal analysis tool. Whenever you need to understand WHY something changed, isolate one variable at a time. The flexible budget in managerial accounting is ceteris paribus in action: hold rates constant, change volume, and now you can see whether the variance was caused by volume or by efficiency.
Sensitivity Analysis as Relaxed Ceteris Paribus
Sensitivity analysis asks: “What if we relax ceteris paribus for one variable?” Instead of holding everything constant, you deliberately vary one assumption (price, volume, cost) to see how the outcome shifts. It’s the controlled release of the ceteris paribus constraint.
North: Where this comes from
- Scientific method — controlled experiments isolate one variable
- Latin phrase formalized in economics to simplify multi-variable systems
- ECON-1221 Chapter 2 - Notes from the Textbook (introduces the concept)
East: What opposes this?
- Reality rarely holds other things equal — multiple variables change simultaneously
- The assumption is a simplification that enables analysis but can mislead if the “held constant” variables actually DO change
- What you choose to hold constant determines what you can see — it’s a framing choice, not a neutral act
- Endogenous vs Exogenous Variables (endogenous variables resist being held constant)
South: Where this leads
- Differential Cost (hold constant what doesn’t change between alternatives)
- Costs for Decision Making (ignore costs identical across options)
- Relevant Range (assumptions hold within a band of activity)
- Constant Unit Cost vs Inventory Costing Methods (holding unit cost constant for analysis)
- Cost-Volume-Profit analysis (hold price and cost structure constant, vary volume)
- Flexible budgets (hold rates constant, flex volume)
- Variance analysis (Ch10) — split total variance into price + quantity by holding one variable at standard while measuring the other. The three-column model (AQ×AP | AQ×SP | SQ×SP) is a ceteris paribus pivot: the middle column holds price at standard so you can isolate the quantity effect
- Sensitivity analysis (controlled relaxation of ceteris paribus)
West: What’s similar?
- Controlled variables in scientific experiments
- A/B testing — change one thing, measure the effect
- Debugging — change one thing at a time to isolate the bug
- cost classification (categorizing costs requires holding context constant)