Which statement best describes a common effect of high-frequency trading on liquidity?

• A. They typically reduce liquidity by removing all market makers.
• B. They often provide liquidity by offering rapid matches.
• C. They always profit at the expense of other traders.
• D. They operate only in equity markets.

Answer: (B)

High-frequency trading often provides liquidity by offering rapid matches. These traders use fast algorithms to place and cancel a large number of orders, posting both bids and asks that populate the order book. Because of this continuous quote activity, there are more counterparties available for a given trade, which tends to shorten spreads and make it easier for other traders to execute quickly. In normal conditions, this added activity supports smoother price discovery and faster execution for everyone.

While there are times when ultra-fast trading can pull back liquidity—especially in stressed markets—the common, typical effect is that HFT adds liquidity by enabling rapid matching of buyers and sellers. It's also worth noting that high-frequency trading is not limited to equity markets; it operates across futures, options, currencies, and other venues.