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How Does High Frequency Trading (HFT) Impact Markets?

By Inyoung Hwang · June 14, 2021 · 4 minute read

We’re here to help! First and foremost, SoFi Learn strives to be a beneficial resource to you as you navigate your financial journey. Read more We develop content that covers a variety of financial topics. Sometimes, that content may include information about products, features, or services that SoFi does not provide. We aim to break down complicated concepts, loop you in on the latest trends, and keep you up-to-date on the stuff you can use to help get your money right. Read less

How Does High Frequency Trading (HFT) Impact Markets?

High-frequency trading (HFT) firms use ultrafast computer algorithms to conduct large trades in markets like stocks, options and futures. HFT firms also rely on sophisticated data networks to get price information and detect trends in markets.

How high-frequency trading impacts markets is a controversial topic. HFT critics argue such firms are an example of how bigger, better funded players have an advantage over smaller retail investors in markets. Meanwhile, proponents of HFT say that these firms add liquidity to markets, helping bring down trading costs for everyone.

No matter what your opinion, HFT is a key part of markets today. Estimates put the percentage of trades in the stock market executed by HFT firms at 50%. So it’s important for even mom-and-pop investors to be aware of these players. Here’s a closer look.

What is High Frequency Trading?

Ultrafast speeds are paramount for high-frequency trading firms. Executing trades at nanoseconds faster can mean the difference between profits and losses for HFT firms.

There are broadly two types of HFT, although many firms are secretive about their trading and technology strategies. The first type is looking for trading opportunities that depend on market conditions. For instance, HFT firms may try to arbitrage price differences between exchange-traded funds (ETFs) and futures that track the same underlying index.

Futures contracts based on the S&P 500 Index may experience a price change nanoseconds faster than an ETF that tracks the same index. An HFT firm may capitalize on this price difference by using the futures price data to anticipate a price move in the ETF.

Another type of HFT is market making. Not all market makers are HFT firms, but market making is one of the businesses some HFT firms engage in.

A big market-making business for HFT firms is payment for order flow (PFOF). This is when retail brokerage firms send their client orders to HFT firms to execute. The HFT firms then make a payment to the retail brokerage firm.

How HFT Makes Money

Bid-Ask Spreads 101

High-frequency trading firms often profit from bid-ask spreads–the difference between the price at which a security is bought and the price at which it’s sold.

For instance, an HFT may provide a price quote for a stock that looks like this: $5-$5.01, 500×600. That means the HFT firm is willing to buy 500 shares at $5 each–the bid–while offering to sell 600 shares at $5.01–the ask. The 1 cent difference is how the market maker makes a profit. While this seems small, with millions of trades, the profits can be sizable.

How wide bid-ask spreads are is also a marker of market liquidity. Bigger chunkier spreads are a sign of less liquid assets, while smaller, tighter spreads can indicate higher liquidity.

Payment For Order Flow 101

When it comes to payment for order flow, high-frequency traders can make money by seeing millions of retail trades that are bundled together.

This can be valuable data that gives HFT firms a sense of which way the market is headed in the short-term. HFT firms can trade on that information, taking the other side of the order and make money.

Background on High Frequency Trading

High-frequency trading became popular when different stock exchanges started offering incentives to firms to add liquidity to the market. Liquidity is the ease with which trades can be done without affecting market prices. The HFT industry grew rapidly after starting to take off in the mid-2000s.

Adding liquidity means being willing to take the other sides of trades and not needing to get trades filled immediately. In other words, you’re willing to sit and wait. Meanwhile, taking liquidity is when you’re seeking to get trades done as soon as possible.

During 2009, about 60% of the market was said to be HFT. Since then, that percentage has declined to about 50% as some HFT firms have struggled to make money due to ever-increasing technology costs and a lack of volatility in some markets. Nowadays, the HFT industry is dominated by a handful of trading firms.

The Debate Over High Frequency Trading

Criticism of HFT

High-frequency trading firms are considered institutional investors because they’re made up of professionals. One complaint about HFT is that it’s giving institutional investors an advantage because they can afford to develop rapid-speed computer algorithms and purchase extensive data networks.

Critics argue that HFT can add volatility to the market, since algorithms can make quick decisions without the judgment of humans to weigh on different situations that come up in markets.

For instance, after the so-called “Flash Crash” on May 6, 2010, when the S&P 500 dropped dramatically in a matter of minutes, critics argued that HFT firms exacerbated the selloff.

HFT critics also argue that such traders only provide liquidity when it’s beneficial to them and then vanish when the market needs it most. A December 2020 paper published by the European Central Bank also argued that too much competition in the HFT industry can cause firms to engage in more speculative trading, which can harm market liquidity.

Defense of HFT

Defenders of high-frequency trading argue that it has improved liquidity and decreased the cost of trading for small, retail investors. In other words, it made markets more efficient.

This can be particularly important in markets like options trading, where there are thousands of different types of contracts that brokerages may have trouble finding buyers and sellers for. HFT can be helpful liquidity providers in such markets.

When it comes to payment for order flow, defenders of HFT also argue that retail investors have enjoyed price improvement, when they get better prices than they would on a public stock exchange.

The Takeaway

It’s tough to be an investor in many markets today without being affected by high-frequency trading. HFT firms are proprietary trading firms that rely on ultrafast computers and data networks to execute large orders, primarily in stocks, options and futures markets.

HFT proponents argue that their participation helps markets be more efficient, since they’re willing buyers and sellers in many trades. Critics argue that they have a big advantage over smaller investors, given how much they pay for information and data networks.

SoFi earns a small amount of money from payment for orders flow that is routed to HFT firms or market makers. This process allows SoFi Invest users to trade without commission fees. Investors can use SoFi’s brokerage services with the Active Investing platform, which allows members to buy and sell stocks, ETFs and fractional shares.

Open a SoFi Invest account today.

Photo credit: iStock/wacomka


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