How does high-frequency trading affect market quality and what should CFA candidates know about it?
There is a lot of debate about HFT in the news. For the CFA Level I exam, what do I need to know about high-frequency trading? Does it improve or harm market quality? What are the specific mechanisms through which HFT firms operate?
High-frequency trading (HFT) refers to algorithmic strategies that execute thousands of orders in microseconds, profiting from tiny price discrepancies. HFT firms use co-located servers (physically close to exchange matching engines) and ultra-low-latency connections to gain speed advantages.
How HFT Firms Operate:
- Market Making: HFT firms post continuous bid-ask quotes, earning the spread. They adjust quotes in microseconds as conditions change, rarely holding positions for more than seconds.
- Statistical Arbitrage: Algorithms detect temporary mispricings between correlated securities (e.g., an ETF and its underlying basket) and trade to capture the convergence.
- Latency Arbitrage: Exploiting the time lag between price updates across different venues — if the price moves on one exchange, the HFT firm can trade on another before that exchange updates.
Impact on Market Quality:
| Positive Effects | Negative Effects |
|---|---|
| Tighter bid-ask spreads | 'Phantom liquidity' — orders vanish in stress |
| Greater displayed depth | Speed advantage over institutional investors |
| Faster price discovery | Flash crashes (May 2010 type events) |
| Lower execution costs in calm markets | Front-running through latency arbitrage |
Example: Suppose Kessler Investments (fictional) submits a buy order for 10,000 shares on exchange A. An HFT firm detects this order and, within microseconds, buys on exchange B (where the price has not yet moved) and sells to Kessler at a slightly higher price. This latency arbitrage transfers a small cost from Kessler to the HFT firm.
Regulatory Responses:
- Speed bumps (e.g., IEX's 350-microsecond delay)
- Minimum resting times for orders
- Enhanced surveillance of spoofing and layering
Exam Focus: The CFA curriculum presents a balanced view — HFT improves liquidity in normal conditions but may reduce it during market stress. Understand both the benefits and the concept of 'phantom liquidity.'
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