How can cost allocations distort segment profitability, and how would you report to avoid bad decisions?

Allocated shared/corporate costs (IT, HR, central overhead) are often spread by a simple key like revenue or headcount that doesn't reflect actual consumption, so a segment can look unprofitable purely because it carries a large arbitrary allocation — and management might wrongly cut or exit it. The fix is to report profitability in tiers: start with revenue less directly attributable variable costs to show contribution margin, then deduct directly controllable fixed costs to show a segment's controllable/direct profit, and only then show allocated corporate costs as a separate, clearly-labelled line to reach fully-loaded profit. Decisions about whether a segment 'earns its keep' should focus on contribution and directly attributable costs — because shutting a segment rarely removes the allocated corporate cost (it just reallocates to the survivors). Where allocation is needed, use activity-based drivers that reflect real consumption. The principle: separate controllable from allocated, and don't let an allocation key drive a strategic exit decision.