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M21.L03 — Signalling and Screening

Module: Module 21 — Information Asymmetry and Synthesis Lesson: L03 of 05 Duration: ~30 minutes Level: Intermediate Provenance: Intermediate Microeconomics with Excel (Barreto) | MIT OCW 14.01 Principles of Microeconomics

Learning Objective

Distinguish between signalling and screening solutions to asymmetric information.

Signalling and Screening

Michael Spence's job market signalling model shows how education can signal ability:

  • High-ability workers get education more easily (lower cost)
  • Firms interpret education as signal of ability
  • Separating equilibrium emerges where only high-ability get educated

Screening occurs when uninformed parties design mechanisms to reveal information:

  • Insurance companies offer menu of contracts
  • Employers use probation periods

Australian applications:

  • HECS/HELP student loan system
  • Job application processes
  • Bank loan screening

Formally, for signalling to work, Riley condition must hold: c_H(e) < c_L(e) for all e, where c is cost of signal.

Worked Example

[Australian context]

Australian universities use ATAR scores as signals:

  • High-ability students can achieve high ATAR at lower effort cost
  • Universities set admission thresholds that only high-ability students meet
  • This creates separating equilibrium where ATAR signals ability

If ATAR became too easy to achieve (costs equalized), it would lose signalling value.

Common Misconception

"Education only has signalling value"

Correction: Education has both human capital and signalling value. The signalling model shows how even with zero human capital benefit, education could still be valuable.

Key Takeaways

  • Signalling comes from informed party (worker)
  • Screening comes from uninformed party (employer)
  • Signals must be costly in a way that differs by type
  • Australian higher education combines both functions

Practice

  1. Why might Australian law firms value law degrees more than consulting firms?
  2. How could an Australian insurer screen high-risk vs low-risk drivers?
  3. Calculate the minimum education cost differential needed to sustain signalling.

Further Resources

Provenance: Intermediate Microeconomics with Excel (Barreto) | MIT OCW 14.01 Principles of Microeconomics