The ECB built an AI tool that reads Reddit to track retail investor mood
The European Central Bank has launched an AI-based indicator that analyzes Reddit posts to measure retail investor sentiment and predict next-day market movements.
In a blog post published November 12, 2026, titled "Reading the room: what Reddit tells us about retail investor sentiment," the ECB detailed an innovative AI tool designed to convert online investing discussions into a sentiment signal tied to next-day market returns. The approach addresses how retail investors increasingly behave like speculative traders who publicly share their market views.
How the Reddit indicator works
The Reddit Retail Investor Sentiment Indicator (R-RISI) is built on research by Fabian Wagner and Julian Metzler, published in August 2026 as ECB Working Paper Series No. 3276. Their dataset includes 8-9 million Reddit posts from 14 investing subreddits such as r/wallstreetbets, r/stocks, and r/investing, spanning 2015 through April 2026.
The researchers employed ChatGPT-5.1 to classify each post's sentiment and identify discussed topics. The large language model outperformed finance-specific models like FinBERT in handling informal language and sentiment classification, making it particularly effective for analyzing retail investor discussions.
The tool generates a daily index of retail investor mood that can be applied across various asset classes and individual securities, providing central banks with real-time insights into market sentiment.
What the numbers show
The research reveals a significant correlation between changes in R-RISI and next-day market returns. This relationship strengthens dramatically during market drawdowns, with the indicator showing a 3.4 times stronger correlation with S&P 500 returns than during calmer periods. This early warning capability is particularly valuable for policymakers monitoring financial stability.
The relationship gets much stronger when markets turn ugly. During market drawdowns, changes in the indicator showed a 3.4 times stronger correlation with S&P 500 returns than during calmer periods.
Why a central bank cares
The ECB's interest stems from structural changes in financial markets, where digital platforms have drawn more retail investors with increasingly speculative trading behaviors. These investors discuss and reinforce their views publicly, creating a valuable data source for monitoring collective sentiment that could amplify price swings during market stress.
Traditional sentiment gauges like surveys often lag behind fast-moving online conversations, making the Reddit indicator particularly useful for detecting emerging market conditions early. The ECB's adoption of a general-purpose AI tool rather than a specialized financial model suggests central banks are becoming more comfortable with off-the-shelf AI solutions for market analysis.
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