← Economics Labs

Lemons Market

Adverse selection collapse under information asymmetry

Buyers see no quality; they offer the price of an average car. At that offer only below-average sellers accept, so buyers re-price, more sellers leave, the price falls again. Watch the unraveling iterate toward either partial trade or total collapse.

Fixed-point: P=γE[qqP]P = \gamma\,\mathbb{E}[q \mid q \leq P]
Buyers cannot observe quality, only bet on the pool. Every time buyers lower their offer, the sellers with better cars withdraw, pushing average quality down, which justifies a still-lower offer. Unraveling. Akerlof (1970).

Quality vs. willingness

P* = 0.0002468101214160246810121416quality qvalue / pricebuyer γ·qseller q

Price iteration

iterationoffer Pq_min
equilibrium P*
0.000
fraction traded
0.0%
avg. quality traded
0.000
surplus vs. efficient
0.0%

Widen the quality spread or drop γ and watch the market unravel — high-quality sellers withdraw first, dragging the buyer’s conditional expectation down, dragging the price down, until only the floor remains.

Lemons Market — Economics Labs · hbar.university