Product × Finance × AI: Financial Products in the Age of AIPart Three AI: how much an agent can do on people's behalf中文
Chapter 23

The special constraints of financeMarkets respond, and mistakes are hard to undo

In most fields, the better an agent works, the more its principal gains. Finance differs in four ways. First, the baseline for comparison should be the actual behaviour of individual investors, not the standard workflow of professionals; many people do no research at all, so an agent changes the depth of their research rather than the time it takes. Second, the market responds: the more people use the same kind of analysis, the less that analysis earns, and any edge in prediction shrinks as it spreads. Third, trading errors are hard to undo; a single mistake can cause enormous losses within minutes. Fourth, many agents use similar methods to reach similar judgments, and may act in the same direction at the same moment. The lasting value of a financial agent therefore lies not in prediction but in lowering costs, maintaining discipline, reducing behavioural bias, and making possible what people could not otherwise do.

1. The baseline for comparison: what users actually do

Three kinds of delegation are common in finance: researching companies, placing trade orders and managing portfolios. Their amplification factors depend first of all on the baseline. Measured against the standard workflow of professionals, research and portfolio management both have high theoretical factors; measured against what individual investors actually do, the conclusion is entirely different. Laarits and Wurgler (2025) estimate that the median time an individual investor spends on research per trade is only about 6 minutes. A research agent mainly changes the depth of research, not the time spent. Placing an order takes only half a minute to begin with, so an agent can save little more than ten seconds. The value of a portfolio management agent is that people who would not otherwise allocate systematically can diversify and rebalance on a schedule.

The baseline decides how much can be saved

Three kinds of financial delegation. Switch the baseline: the standard workflow of professionals, or the actual behaviour of individual investors.

Log scale, in minutes of the principal's time. The standard workflow and the time spent after delegation are theoretical values estimated by the author. The median time individual investors spend on research per trade is about 6 minutes; see Laarits and Wurgler (2025). After adopting a robo-adviser, investors did not log in or trade less; see D'Acunto, Prabhala and Rossi (2019).

2. The market responds: the returns to analysis fall as it spreads

In other fields, when a technology lets everyone work better, everyone benefits. Investment research is different. Grossman and Stiglitz (1980) showed that information earns a return only because acquiring it is costly: the more people use the same kind of analysis, the faster the same information enters prices and the smaller the excess return each person can earn, until it barely covers the cost of the analysis. Once AI drives down the cost of analysis, more people will use the same kind of analysis, and its excess return will fall accordingly. The fundamental law of active management gives the other side of the same conclusion (Grinold, 1989). The most direct effect of AI is to widen breadth cheaply, covering thousands of stocks at once and reassessing them every day. But breadth raises the information ratio only by its square root: ten times as many independent judgments raise the information ratio only about threefold. And the information coefficient itself falls as the same kind of analysis spreads, offsetting even that gain. In a market close to efficient, the benefit of an agent that predicts more accurately is limited, and it shrinks as such agents spread.

When analysis becomes cheap, where do its returns go?

The more investors use the same kind of analysis, the faster the same information enters prices and the smaller the excess return each user earns. People keep joining until the excess return only just covers the cost of analysis.

AI makes analysis cheaper: drag left
Investors using this analysis at equilibrium
Excess return per user

Illustrative model following the logic of Grossman and Stiglitz (1980): the total value of the information is 4% a year; the more users, the earlier the information enters prices, and the excess return per user falls proportionally; at equilibrium the excess return equals the cost of analysis. The numbers do not correspond to estimates for any market.

3. Which terms of return an agent can affect

Return to the decomposition of realized return: time compensation, risk compensation, information advantage, trading costs and luck. An agent cannot create time compensation, nor can it change luck; whatever it contributes to information advantage is consumed by competition. What can last lies in three other places. In risk compensation, it helps users stay diversified, rebalance as planned and not give up in the face of volatility. In trading costs, it chooses suitable order types and timing, reducing spreads and market impact. And between the return users actually earn and the return of the product, it narrows the gap caused by buying high and selling low. None of this depends on predicting better than others, so it does not disappear when everyone uses the same agent.

Which terms of return an agent can affect

Each row is one term of realized return. The bar is the improvement an agent might bring (illustrative). Switch to "After similar agents spread" to see which value competition consumes.

Illustrative. "Behaviour gap" means the gap between the return investors actually earn and the return of the products they hold, which comes mainly from buying high, selling low and market timing.

4. From impossible to possible

For many individual investors, the greatest value of an agent is not doing things faster but making feasible what they would not otherwise do. D'Acunto, Prabhala and Rossi (2019) studied a robo-adviser launched by an Indian brokerage. Investors whose holdings had been concentrated and poorly diversified became markedly more diversified after adopting it, and their volatility fell. Investors who had already been fairly diversified ended up holding fewer stocks; their volatility fell slightly, but they traded more often. After adoption, behavioural biases such as the disposition effect and trend chasing also declined. The value of the agent was concentrated among those who had been doing worst; for those who had been doing better, it could also bring new problems.

The value is concentrated among those who were doing worst

Changes in two groups of investors before and after adopting a robo-adviser. Switch between before and after to compare the number of stocks held and portfolio volatility (illustrative numbers).

Illustrative numbers; the directions follow D'Acunto, Prabhala and Rossi (2019), a study of a robo-adviser at an Indian brokerage. Investors who had been poorly diversified became markedly more diversified after adoption, and their volatility fell; investors who had been fairly diversified ended up holding fewer stocks, their volatility fell slightly, and they traded more. The reduction in behavioural biases applied to all adopters.

5. Trading errors are hard to undo

When an information task goes wrong, the error can usually be found and corrected, and the loss is limited. Trading is different: orders are filled within milliseconds, cannot be withdrawn once filled, and errors can be rapidly amplified by leverage and repeated execution. In August 2012, a deployment error in the trading system of a US market maker caused it to send millions of erroneous orders in about 45 minutes. It lost about $460 million and was subsequently acquired (U.S. Securities and Exchange Commission, 2013). Authority for financial agents must therefore be tiered: providing information and advice can be autonomous; changing holdings and moving funds require the person's own confirmation, together with per-transaction and cumulative limits and a switch that stops everything at once when something abnormal happens.

45 minutes of erroneous orders

A deployment error leaves a trading system sending erroneous orders without pause. Play the cumulative loss; then switch on "cumulative loss limit and stop switch" to see the consequences of the same error.

Time elapsed
Cumulative loss

Based on the U.S. Securities and Exchange Commission's 2013 order on an incident in August 2012 (Release No. 34-70694): millions of erroneous orders were sent in about 45 minutes, with a loss of about $460 million. The path of the loss over time is illustrative; the limit of $10 million is also illustrative.

6. Many agents acting together

When many investors use similar models, similar data and similar rules, their trades will also be similar. Khandani and Lo (2011) analysed the "quant crisis" of August 2007: quantitative funds following similar strategies unwound their positions at the same time within a few days; their selling pushed prices down and forced still more funds to unwind. Kirilenko et al. (2017), studying the "flash crash" of May 2010, likewise showed that high-frequency traders passed positions back and forth among themselves during the fall, amplifying price swings. The spread of AI agents may amplify this sameness: each agent's rules may be reasonable, yet when all agents execute the same rule at the same time, the result can be bad for everyone.

Many agents using the same rule

Fifty agents each manage a portfolio, and each has a rule to "cut the position when the fall exceeds a certain size". Drag how similar the rules are, then trigger a 3% fall, and see how many agents sell at the same time and how far the price falls in the end.

Agents selling at once
Total price fall

Illustrative model: when rules are similar, the agents' selling thresholds cluster around 3%; each agent's sale pushes the price down a further 0.15%, which may trigger more agents to sell; beyond a certain level of similarity, cascading sales appear suddenly. For an actual case of similar strategies unwinding at once, see Khandani and Lo (2011); for the 2010 flash crash, see Kirilenko et al. (2017).

7. Implications for product design

The value of a financial agent is not sold on prediction; it lies in cost, discipline, behaviour and access. Execution needs tiered authority and limits, and must take into account the consequences of many agents acting at once.

Chapter summary: the value and limits of financial agents

Four design requirements, each corresponding to one mechanism in this chapter.

The baseline is actual behaviourMeasure value against what users did before

A research agent's value lies in depth; a portfolio agent's value lies in letting people who do no allocation do it, not in saving a few minutes.

The value of prediction falls as it spreadsDo not sell on prediction

Place value in staying diversified, lowering costs and reducing behavioural bias, which do not disappear as similar agents spread.

Trading errors are hard to undoTier authority; set limits and a stop switch

Information and advice can be autonomous; changing holdings and moving funds need the person's confirmation, with per-transaction and cumulative limits.

Agents act togetherKeep similar rules from firing at once

Stagger execution times, vary rule parameters, and when markets swing violently, flag the risk and slow execution down.

References