Disruptive Innovation (Christensen, 1997) 破壞式創新

Disruptive Innovation theory explains how smaller firms with fewer resources can successfully challenge established incumbents. Disruption occurs when entrants target overlooked segments (low-end or non-consumers) with simpler, cheaper offerings, then move upmarket as performance improves. Incumbents rationally focus on profitable mainstream customers and fail to respond until it is too late.

Trigger conditions:

• User asks why a startup with an inferior product is gaining market share
• User needs to evaluate whether a new entrant is a disruptive or sustaining threat
• User wants to design a market entry strategy targeting overserved customers
• User mentions "disruption", "low-end market", or "good enough product"

When NOT to use:

• For sustaining innovation management (incremental improvements) -> use stage-gate or innovation funnel
• For platform-based competition -> use grad-platform-economics
• For analyzing national-level innovation systems -> use grad-diamond

IRON LAW: Disruption Comes from BELOW

Disruption originates from the LOW END or NEW MARKET — never from a
superior product attacking head-on. Incumbents fail because they
OVER-SERVE mainstream customers, creating a performance overshoot that
opens space for simpler, cheaper alternatives.

If the entrant competes on the SAME performance dimensions as the
incumbent, it is sustaining innovation — NOT disruption.

• Performance trajectories improve faster than customer needs evolve
• Incumbents are rational — they chase higher margins upmarket
• Disrupted markets have identifiable overserved segments

Step 1: Map Performance Trajectories

Plot the incumbent's performance improvement trajectory against the range of customer needs (low-end to high-end). Identify where performance overshoots what mainstream customers can absorb.

Step 2: Identify the Foothold

Classify the entrant's strategy:

• Low-end foothold: Targets overserved customers with a cheaper, simpler, "good enough" product (e.g., discount airlines vs full-service carriers)
• New-market foothold: Targets non-consumers who previously could not access the product at all (e.g., personal computers vs mainframes)

Step 3: Assess Disruption Potential

Evaluate three conditions:

1. Performance overshoot exists — mainstream customers do not use all features they pay for
2. Entrant has an upmarket migration path — the simpler product can improve over time
3. Incumbent has asymmetric motivation — responding means cannibalizing high-margin business

Step 4: Recommend Response Strategy

For incumbents: autonomous business unit, acquire the disruptor, or create own low-end offering. For entrants: stay below the radar, improve incrementally, move upmarket only when ready.

# Disruption Assessment: {Industry/Company}

• For mathematical formalization of performance trajectories, see references/performance-trajectory-model.md
• For case studies (steel minimills, disk drives), see references/disruption-cases.md