With the rapid development of financial technology and electronic trading systems, algorithmic trading and high-frequency trading (HFT) have gradually become important trading forms in global capital markets. High-frequency trading utilizes high-speed computing power and low-latency network infrastructure to execute large volumes of trading orders within milliseconds or even microseconds, thereby capturing extremely short-lived price movements in the market and profiting from small price differentials. Over the past decade, this trading model has expanded rapidly and has gradually reshaped the trading structure and liquidity patterns of capital markets.
Under normal market conditions, high-frequency trading can enhance market liquidity, facilitate price discovery, and narrow bid-ask spreads, thereby contributing positively to market efficiency. However, during periods of heightened market volatility or when trading systems experience malfunctions, high-frequency trading may amplify price fluctuations and even lead to short-term market disruptions. For example, the “Flash Crash” in the United States in 2010 and the Knight Capital incident in 2012 demonstrated that without adequate risk controls, high-frequency trading can have significant impacts on markets within extremely short periods of time.
In recent years, regulatory authorities across jurisdictions have gradually established regulatory frameworks to address both the opportunities and risks brought about by high-frequency trading. Major capital markets around the world generally strengthen market supervision and risk management through measures such as reporting or registration systems, controls on trading speed and order flow, circuit breakers and price stabilization mechanisms, as well as differentiated fee structures for high-frequency trading accounts. Taiwan’s securities market does not adopt a reporting or registration system specifically for high-frequency traders. Instead, regulatory measures mainly focus on market surveillance, controls on trading speed and order flow, and price stabilization mechanisms to mitigate the impact of abnormal trading activities and maintain market stability and order.
Overall, the impact of high-frequency trading on markets is two-sided. On the one hand, it improves trading efficiency and market liquidity; on the other hand, it may increase the complexity of market structures and introduce potential risks. As trading technologies continue to advance and cross-market trading activities become increasingly frequent in global financial markets, understanding the development and regulatory experiences of high-frequency trading in international markets has become an important topic.
This article explains the development and regulatory trends of high-frequency trading in major international capital markets and further describes the trading supervision mechanisms of Taiwan’s securities market.
The Emergence and Operational Mechanisms of High-Frequency Trading
High-frequency trading is generally regarded as a form of algorithmic trading. Its key characteristics include the use of high-speed computing systems and low-latency networks to submit and cancel large volumes of orders within extremely short periods of time in order to capture small and short-lived price differences in the market. Such trading heavily relies on automated algorithms and advanced information technology infrastructure to gain speed advantages.
Internationally, there is no single unified definition of high-frequency trading. For example, U.S. regulators typically identify high-frequency trading based on trading behavior characteristics, including high-speed algorithmic order placement, large numbers of order submissions and cancellations, extremely short holding periods, and predominantly intraday trading. In the European Union, under the MiFID II framework, high-frequency trading is classified as a subset of algorithmic trading and is defined based on factors such as message traffic and the infrastructure used. Japan, on the other hand, has introduced explicit legal provisions requiring high-frequency traders to register and be subject to regulatory oversight.
In terms of trading strategies, high-frequency trading commonly involves market-making, arbitrage between derivatives and spot markets, cross-market arbitrage, and pair trading strategies based on price relationships between related assets. The core logic of these strategies is to accumulate small profits from minimal price differences through extremely high trading frequency. Because the profit from each individual trade is typically small, high-frequency trading relies on large trading volumes and highly efficient system operations.
With the widespread adoption of electronic trading technologies, high-frequency trading has developed rapidly in major global markets. The United States is one of the most active markets for high-frequency trading, with some studies suggesting that HFT once accounted for more than half of total equity trading volume. High-frequency trading also represents a significant proportion of trading activity in European markets and plays an important role in providing liquidity and improving price efficiency. In addition to developed Western markets, algorithmic and high-frequency trading have also gained a foothold in Asian markets such as Hong Kong, Japan, and South Korea.
The impact of high-frequency trading on markets is complex. Many studies indicate that HFT can improve market liquidity, narrow bid-ask spreads, and enhance price discovery. However, during periods of extreme market volatility or when trading systems malfunction, high-frequency trading may amplify market fluctuations due to rapid order cancellations or chain reactions among algorithms, potentially causing liquidity to vanish temporarily. Therefore, regulatory authorities worldwide have paid close attention to these potential risks and have established corresponding regulatory mechanisms.
Regulatory Frameworks for High-Frequency Trading in Major International Markets
In response to structural changes in markets brought about by high-frequency trading, major capital markets have gradually established regulatory frameworks that seek to balance market efficiency with financial stability.
Some markets require large traders or high-frequency traders to register or report their activities in order to strengthen the identification of HFT participants and improve information disclosure mechanisms. For instance, the United States monitors large trading activities through the Large Trader Reporting system, while Japan has established a registration system for high-frequency traders that allows regulators to identify and supervise relevant trading activities.
Regarding trading systems and risk management, the European Union’s MiFID II requires institutions engaged in algorithmic and high-frequency trading to establish robust risk control and system testing mechanisms to ensure that trading systems have sufficient capacity and stability and can promptly halt trading under abnormal circumstances. Trading venues are also required to provide testing environments and monitoring mechanisms to prevent algorithmic trading failures from disrupting market order.
In terms of market stability mechanisms, most major markets have implemented price stabilization measures, such as individual security circuit breakers, market-wide circuit breakers, or volatility interruption mechanisms, to prevent excessive short-term price fluctuations. Some markets also impose limits on order flow, set maximum order-to-trade ratios, or adopt differentiated fee structures to reduce the burden that frequent order submissions and cancellations may place on market systems.
Certain regulatory mechanisms also emphasize monitoring and tracking trading behavior, such as requiring the retention of trading records, marking algorithmic orders, strengthening data reporting requirements, and preventing market manipulation. These measures enable regulatory authorities to more effectively analyze and manage high-frequency trading activities.
Overall, international regulatory trends for high-frequency trading focus on enhancing market transparency, strengthening risk controls for trading systems, and maintaining market stability. In an environment where financial technology and electronic trading continue to evolve rapidly, regulatory authorities worldwide continue to adjust regulatory frameworks and related measures to ensure that an appropriate balance is maintained between promoting market efficiency and safeguarding stability.
Abnormal HFT Cases and Market Risks
With the rapid growth of high-frequency trading in global capital markets, while it has contributed to trading efficiency and liquidity provision, certain historical events have shown that it may also intensify market volatility, highlighting risks that cannot be ignored. Among the most notable cases are the 2010 “Flash Crash” in the United States and the 2012 Knight Capital incident, both of which demonstrated that high-frequency and algorithmic trading, when lacking adequate risk controls, may cause significant market disruptions within extremely short periods.
On May 6, 2010, the U.S. stock market experienced dramatic volatility within just a few minutes, during which the Dow Jones Industrial Average plunged nearly 1,000 points before quickly recovering. The Flash Crash was triggered by a large institutional sale of stock index futures, which rapidly drove down futures prices. Subsequently, algorithmic and high-frequency trading strategies executed arbitrage trades, causing related equities to be sold in large volumes. The market became flooded with sell orders while buy orders were scarce, resulting in a sudden collapse in liquidity and a sharp drop in stock prices. This event highlighted how liquidity in highly automated trading environments can disappear rapidly, amplifying market turbulence.
Another significant case occurred in 2012 involving the market-making firm Knight Capital. Due to an error in a system update and the absence of mechanisms to prevent abnormal order submissions, the firm’s algorithm continuously sent large volumes of buy and sell orders shortly after the market opened. This led to abnormal price movements in several stocks. Within approximately 45 minutes, the firm incurred trading losses exceeding USD 400 million, ultimately causing severe financial distress. This incident demonstrated that algorithmic trading systems lacking adequate testing and risk control mechanisms may pose substantial risks both to markets and to the institutions themselves.
Taken together, these cases show that while high-frequency trading can enhance market efficiency, in highly automated and high-speed trading environments, deficiencies in algorithm design, system testing, or risk control may lead to market disruptions within extremely short periods. Consequently, regulatory authorities worldwide have implemented mechanisms such as circuit breakers, enhanced trading monitoring, and stricter risk control requirements for algorithmic trading to reduce the likelihood of similar incidents and maintain market stability and investor confidence.
Trading Supervision Mechanisms in Taiwan’s Securities Market
Compared with certain markets that adopt reporting or registration systems for high-frequency traders, Taiwan’s securities market does not employ such mechanisms. Instead, Taiwan has established a range of order flow and price protection mechanisms, along with various supervisory and control measures that are broadly consistent with international regulatory trends.
In situations where markets experience significant volatility, negative shocks, or system abnormalities, measures such as order-line traffic limits can effectively control sudden surges in order submissions. Intraday price stabilization mechanisms and daily price limits help curb excessive price fluctuations and reduce trading risks. In addition, the investor identification (ID) monitoring mechanism enables regulators to track investors’ trading activities effectively and in real time, allowing relevant authorities to conduct comprehensive analyses of market conditions and unexpected events.
Although Taiwan’s market has not developed high-frequency trading activities on the same scale as those seen in European and American markets, with the continued advancement of trading technologies, new forms of trading behavior may emerge alongside HFT. Observing such developments and international regulatory trends—while balancing market efficiency and stability—will help further refine Taiwan’s market systems and policies, thereby promoting the healthy development of the securities market.
Conclusion
Based on developments in international markets and the current situation in Taiwan, high-frequency trading has become an important component of the trading structure in global capital markets. Through high-speed computing and automated trading strategies, high-frequency trading contributes positively to market liquidity, price discovery, and the narrowing of bid-ask spreads. However, in highly automated and high-speed trading environments, insufficient risk control and regulatory mechanisms may amplify market volatility and even lead to short-term market disruptions. Consequently, regulatory authorities around the world generally adopt regulatory approaches that seek to balance market efficiency with financial stability.
Major securities markets internationally have implemented various measures to strengthen the management of high-frequency trading, including registration or reporting systems for HFT participants, risk control mechanisms for algorithmic trading, market circuit breakers and price stabilization measures, and enhanced trading monitoring and data reporting systems. These measures help promote market efficiency while mitigating the systemic risks that may arise from high-frequency trading.
Looking ahead, as trading technologies continue to evolve, high-frequency trading may play an increasingly important role in global markets. Achieving an appropriate balance between promoting market efficiency and maintaining market stability will remain a key challenge for securities markets worldwide.