Context
Porsche secretly accumulated a 74.1% economic stake in VW through cash-settled derivatives, avoiding disclosure requirements. VW was the world's most shorted stock. When Porsche revealed its position, the short squeeze sent VW's share price from €200 to €1,005 in two days — briefly making it the world's most valuable company.
Exam Question
What does the Porsche/VW case illustrate about limits to arbitrage?
Short-selling requires borrowing shares. When the free float collapses (only ~1% of VW shares were freely tradeable after Porsche's disclosure), short-sellers cannot cover their positions — creating a catastrophic short squeeze. This is the 'synchronisation risk' and 'noise trader risk' that prevents arbitrageurs from correcting mispricing.
Key Details