Friday, March 03, 2023

Applying Corrective AI to Daily Seasonal Forex Trading


By Sergei Belov, Ernest Chan, Nahid Jetha, and Akshay Nautiyal



We applied Corrective AI (Chan, 2022) to a trading model that takes advantage of the intraday seasonality of forex returns. Breedon and Ranaldo (2012)  observed that foreign currencies depreciate vs. the US dollar during their local working hours and appreciate during the local working hours of the US dollar. We first backtested the results of Breedon and Ranaldo on recent EURUSD data from September 2021 to January 2023 and then applied Corrective AI to this trading strategy to achieve a significant increase in performance.

Breedon and Ranaldo (2012) described a trading strategy that shorted EURUSD during European working hours (3 AM ET to 9 AM ET, where ET denotes the local time in New York, accounting for daylight savings) and bought EURUSD during US working hours (11 AM ET to 3 PM ET). The rationale is that large-scale institutional buying of the US dollar takes place during European working hours to pay global invoices and the reverse happens during US working hours. Hence this effect is also called the “invoice effect".


There is some supportive evidence for the time-of-the-day patterns in various measures of the forex market like volatility (see Baille and Bollerslev(1991), or Andersen and Bollerslev(1998)), turnover (see Hartman (1999), or Ito and Hashimoto(2006)), and return (see Cornett(1995), or Ranaldo(2009)).  Essentially, local currencies depreciate during their local working hours for each of these measures and appreciate during the working hours of the United States.


Figure 1 below describes the average hourly return of each hour in the day over a period starting from 2019-10-01 17:00 ET to 2021-09-01 16:00 ET. It reveals the pattern of returns in EURUSD. The return pattern in the above-described “working hours'' reconciles with the hypothesis of a prevalent “invoice effect” broadly. Returns go down during European working and up during US working hours.


Figure 1: Average EURSUD return by time of day (New York time)


As this strategy was published in 2012, it offers ample time for true out-of-sample testing. We collected 1-minute bar data of EURUSD from Electronic Broking Services (EBS) and performed a backtest over the out-of-sample period October 2021-January 2023. The Sharpe Ratio of the strategy in this period is  0.88, with average annual returns of 3.5% and a maximum drawdown of -3.5%. The alpha of the strategy apparently endured. (For the purpose of this article, no transaction costs are included in the backtest because our only objective is to compare the performances with and without Corrective AI, not to determine if this trading strategy is viable in live production.)


Figure 2 below shows the equity curve (“growth of $1”) of the strategy during the aforementioned out-of-sample period. The cumulative returns during this period are just below 8%. We call this the “Primary” trading strategy, for reasons that will become clear below.





Figure 2: Equity curve of Primary trading strategy in out-of-sample period


What is Corrective AI?

Suppose we have a trading model (like the Primary trading strategy described above) for setting the side of the bet (long or short). We just need to learn the size of that bet, which includes the possibility of no bet at all (zero sizes). This is a situation that practitioners face regularly. A machine learning algorithm (ML) can be trained to determine that. To emphasize, we do not want the ML algorithm to learn or predict the side, just to tell us what is the appropriate size.

We call this problem meta-labeling (Lopez de Prado, 2018) or Corrective AI (Chan, 2022) because we want to build a secondary ML model that learns how to use a primary trading model.

We train an ML algorithm to compute the “Probability of Profit” (PoP) for the next minute-bar. If the PoP is greater than 0.5, we will set the bet size to 1; otherwise we will set it to 0. In other words, we adopt the step function as the bet sizing function that takes PoP as an input and gives the bet size as an output, with the threshold set at 0.5.  This bet sizing function decides whether to take the bet or pass, a purely binary prediction.

The training period was from 2019-01-01 to 2021-09-30 while the out-of-sample test period was from 2021-10-01 to 2023-01-15, consistent with the out-of-sample period we reported for the Primary trading strategy. The model used to train ML algorithm was done using the Corrective AI (CAI) API, with more than a hundred pre-engineered input features (predictors). The underlying learning algorithm is a gradient-boosting decision tree.

After applying Corrective AI, the Sharpe Ratio of the strategy in this period is 1.29  (an increase of 0.41), with average annual returns of 4.1% (an increase of 0.6%)  and a maximum drawdown of -1.9% (a decrease of 1.6%). The alpha of the strategy is significantly improved.


The equity curve of the Corrective AI filtered secondary model signal can be seen in the figure below.


Figure 3: Equity curve of Corrective AI model  in out-of-sample period

Features used to train the Corrective AI model include technical indicators generated from indices, equities, futures, and options markets. Many of these features were created using Algoseek’s high-frequency futures and equities data. More discussions of these features can be found in (Nautiyal & Chan, 2021).




By applying Corrective AI to the time-of-the-day Primary strategy, we were able to improve the Sharpe ratio and reduce drawdown during the out-of-sample backtest period. This aligns with observations made in the literature on meta-labeling for our primary strategies. The Corrective AI model's signal filtering capabilities do enhance performance in specific scenarios.




We are grateful to Chris Bartlett of Algoseek, who generously provided much of the high-frequency data for our feature engineering in our Corrective AI system. We also thank Pavan Dutt for his assistance with feature engineering and to Jai Sukumar for helping us use the CAI API. Finally, we express our appreciation to Erik MacDonald and Jessica Watson for their contributions in explaining this technology to’s clients




Breedon, F., & Ranaldo, A. (2012, April 3). Intraday Patterns in FX Returns and Order Flow.

Chan, E. (2022, June 9). What is Corrective AI? Retrieved February 23, 2023, from

Lopez de Prado, M. (2018). Advances in Financial Machine Learning. Wiley.

Nautiyal, A., & Chan, E. (2021). New Additions to the Factor Zoo. Retrieved February 28, 2023, from



Joen Vick said...

This is a very interesting post.

Anuj Kumar Prajapati said...

Great Content, thanks for sharing this article

MonsieurMagique said...

How robust would this ML optimised approach be to overfitting?

Ernie Chan said...

All numbers reported are out-of-sample, so minimal overfitting.

MonsieurMagique said...

Very good!

Anonymous said...

Nice post !

Solidary Prime said...

Each day, AI is included more in our daily lives, so of course it is going to affect trading. Such an interesting post!