Quiz: Platform Wars

Answer: (B) Learning costs are the cognitive and time costs of adapting to a new interface or workflow. They differ from transaction costs (the cost of the migration process itself), loyalty costs (accumulated reward loss), contractual costs (termination fees), and psychological uncertainty (fear of the unknown).

Answer: (B) Winner-take-all requires (i) strong cross-side effects (each new user adds value for the other side) AND (ii) single-homing by at least one side (so users are not on both platforms). If consumers single-home, merchants must join the dominant network to reach them. This feedback loop tips the market.

Answer: (B) The "flywheel" metaphor captures compounding: the advantage does not just persist, it accelerates. Each loop turn strengthens the next. This is why the data flywheel creates such durable moats: a competitor starting 5 years later faces an incumbent whose flywheel has spun 5 years more.

Answer: (B) A Sesame Credit score is a non-transferable, non-portable reputation asset. Unlike passwords or payment data (which can be migrated), a credit score built on Ant's proprietary model cannot be ported to a competitor. Users who leave lose years of accumulated scoring, making the cost of switching uniquely durable.

Answer: (B) Multi-homing on the merchant side means competition on price is intense. Stripe cannot extract monopoly rents because merchants have ready alternatives. This is why Stripe competes primarily on developer experience, API quality, and fraud tools - dimensions where genuine differentiation is possible - rather than on price.

Answer: (B) $y' = k/x' = 2{,

Answer: (C) When ETH doubles (r = 2), impermanent loss $= 2\sqrt{2

Answer: (B) The sandwich: (1) bot buys asset X before victim's buy order executes; (2) victim's trade moves price of X up; (3) bot sells X at higher price. The victim effectively paid a higher price than the pre-trade spot. This is a mechanism failure: the AMM mechanism does not prevent bots from exploiting pending order visibility.

Answer: (B) PFOF creates a principal-agent problem: the broker (agent) is paid by market makers, but should be acting in the user's (principal's) interest. The hidden cost to users is the spread widening - they pay slightly more (buy) or receive slightly less (sell) than the best available price, but this cost is invisible to most users.

Answer: (B) L = (P - MC)/P = (1.00 - 0.15)/1.00 = 0.85. A Lerner index of 0.85 means the platform operates with an 85% price-cost margin. This is high, suggesting significant market power. By comparison, L = 0 means perfect competition; L = 1 means MC is zero and the firm captures all consumer surplus.

Answer: (B) \varepsilon = -1/L = -1/0.5 = -2. A Lerner index of 0.5 corresponds to a price elasticity of -2: for every 1% price increase, the platform loses 2% of demand. This is moderately elastic. Platforms with L = 0.85 face \varepsilon = -1.18 (near unit elasticity).

Answer: (B) The EU found that NFC restriction was an artificial barrier: Apple could have allowed third-party wallet access to NFC without compromising security (as demonstrated by alternatives). Controlling a hardware interface to prevent competition in an adjacent market is abuse of dominant position under EU competition law.

Answer: (B) AISPs can read your bank account data with your consent. This directly attacks the data moat: banks previously had exclusive access to years of your transaction history. PSD2 portability means a challenger bank can access the same data to personalise offers and build credit models.

Answer: (B) Regulators identified two problems: (i) regulatory arbitrage (bank functions without bank capital requirements, creating systemic risk) and (ii) data monopoly (Sesame Credit controlled credit scoring for 500m people, blocking banks from building competing models). The restructuring addressed both: Ant became a financial holding company subject to capital rules, and Sesame data was shared with the PBOC credit bureau.

Answer: (D) Under MiCA, ALL EMTs require authorisation (as e-money institutions or credit institutions). The "no authorisation needed" claim in D is the opposite of MiCA's framework. A, B, C are correct: EMTs peg to single fiat, ARTs reference baskets, and ARTs face stricter rules.

Answer: (A) Alipay payments remained dominant (~85% China mobile payment share). MYbank survived but lost the data-driven 310 model and operates under Basel-equivalent capital. Sesame Credit was dismantled as an external credit bureau but its scoring survives as internal to Ant. The other options are factually incorrect.

Answer: (B) The embedded finance advantage is informational: the platform sees data (daily GMV, return rates, customer acquisition costs) that traditional banks cannot access. This Akerlof advantage - reducing adverse selection in lending - allows better pricing and lower defaults, not just distribution efficiency.

Answer: (B) DeFi follows the new-market disruption pattern: it started by serving users TradFi did not serve (unbanked crypto users, global permissionless users), with a simpler product (AMMs, lending protocols) that TradFi would not build. Whether the disruption continues depends on whether mechanism failures (MEV, hacks, regulatory barriers) are resolved before TradFi adapts.

Answer: (B) This is the key IO insight for AI: sharing data does not share the model's parameters, which encode learned patterns from years of historical data. A competitor who receives one year of ported transaction data cannot replicate the predictive power of a model trained on ten years. The next regulatory frontier is "model sharing" or "model auditability," not just data access.

Answer: (B) All seven lenses apply coherently and reinforce each other. The Sesame score switching cost (Klemperer) amplifies the information moat (Akerlof) that justifies the high Lerner index. This is why the Ant Group case is the definitive fintech economics case: it validates all seven analytical frameworks simultaneously.