The largest single-week net purchase in fifteen years! Citadel analyst: Retail investors are buying AI stocks again

Retail investors are returning to artificial intelligence trading with unusual vigor.

Scott Rubner, Head of Equity and Derivatives Strategy at Citadel Securities, pointed out in his latest research report that last week, retail investors made a net purchase of $9.1 billion in U.S. stocks through the company's platform, marking the largest single-week net purchase in nearly 15 years, with funds highly concentrated in AI-related stocks and ETFs.

This capital inflow pushed both the Nasdaq 100 Index and the S&P 500 Index to new all-time highs, despite persistent market warnings of an AI bubble. For investors focused on the technology sector, the large-scale return of retail participants is becoming a key force supporting the current rally.

Semiconductors and AI infrastructure attract the main inflow of funds

Retail buying last week was highly concentrated. According to Scott Rubner, retail investors made net purchases of around $2.6 billion in semiconductor stocks, making it the third highest single-week purchase in the past year and setting up October to potentially become the biggest month for net inflows into chip stocks on the platform. Meanwhile, AI infrastructure-related stocks also recorded net purchases of about $2.4 billion.

It is noteworthy that these inflows occurred at a time when chip stocks were under pressure and there were doubts in the market about the sustainability of AI prosperity, showing that retail confidence in the AI sector has not been shaken by short-term volatility.

More directional bets, rather than increased trading volume

Rubner emphasized in the report that the expansion in the size of retail buying this time is mainly due to "stronger directional conviction, rather than an overall increase in trading volume." Data shows that retail buying last week exceeded selling by 2.7%, putting directional skew in the 90th percentile of weekly readings over the past year. Meanwhile, overall trading activity remains in the 42nd percentile for the past year, below average.

This combination suggests that retail investors are not broadly chasing rising prices, but are making proactive and concentrated bets on AI, sending a clear signal.

Rubner’s early October prediction confirmed

This return of retail investors was not unexpected. At the beginning of October, Rubner had accurately predicted this trend, pointing out that after the obvious cooldown in September, October would offer investors a better opportunity to "rebuild positions," with the upcoming earnings season and corporate buyback wave set to provide support for the market.

According to a previous report from Bloomberg, Rubner at the time clearly stated that retail cash was being "reloaded," waiting to return to the U.S. stock market. Last week’s data confirmed this view and kept the market highly attentive to whether retail capital can continue to flow into stocks in the future.