---
id: "prereq-unit-economics"
type: "prereq"
source_timestamps: ["§ The 4S Framework"]
tags: ["finance", "metrics"]
related: ["framework-4s", "quote-strategy-liability"]
reason: "The 4S framework requires tracking cost-to-serve, lifetime value, and churn risk to ensure short-term survival and long-term thriving."
sources: ["tail1"]
sourceVaultSlug: "hbr-seg-tail1"
originDay: 1
articleStem: "hbr-tail-117-middle-market"
sourceUrl: "https://hbr.org/2026/03/why-companies-dont-compete-in-the-middle-market"
sourceTitle: "Why Companies Don’t Compete in the Middle Market"
---
# Understanding of Unit Economics

**Why required:** The **'Survive/Thrive'** step of the [[framework-4s]] cannot be executed without fluency in **unit economics**. The source explicitly names the metrics to track: **cost-to-serve, lifetime value, churn risk, and scalability** constraints.

Without this financial fluency, a company might design a delightful experience that is fundamentally unprofitable — a 'liability' rather than a strategy (see [[quote-strategy-liability]]). Practitioners should be comfortable with LTV/CAC, contribution margin, and cohort-level economics before applying the framework.