European Central Bank (ECB) researchers have explained how they use artificial intelligence to measure retail investor sentiment from Reddit discussions. In a November 12, 2026 blog post, Fabian Wagner and Julian Metzler outlined the Reddit Retail Investor Sentiment Indicator (R-RISI), a tool designed to provide more frequent signals about market mood than traditional surveys.
The underlying research is not newly published: ECB Working Paper No. 3276 was released on August 24, 2026. Reuters reported on November 12 that the researchers analyzed more than nine million Reddit posts. The working paper studied posts from 2015 through April 2026, while charts in the new ECB blog include data through October 2026.
The analysis covers discussions across investing, economic and cryptocurrency communities, including r/wallstreetbets, r/stocks, r/investing and r/Bitcoin. OpenAI’s ChatGPT 5.1 was used to classify posts as positive, negative or neutral, identify topics such as equities, tariffs and crypto, and detect the companies or assets being discussed. The researchers’ dashboard describes a full corpus drawn from 14 subreddits.
The index does not simply count bullish and bearish messages. Posts receive greater weight according to their Reddit score and comment activity. Daily positive and negative totals are then compared with their own historical patterns over the previous 365 days. An R-RISI reading is therefore a standardized balance of discussion, not the percentage of Reddit users planning to buy or sell stocks.
The researchers found that market shocks changed what people discussed. Macroeconomic topics became a major negative influence during the COVID-19 market disruption, while tariff-related posts pulled sentiment lower during the April 2025 turmoil. Separate measures for major AI-linked technology stocks and Bitcoin broadly followed market swings, although Bitcoin sentiment diverged from prices more often.
According to the researchers, changes in the index have a statistically significant association with next-day S&P 500 returns, particularly when markets are falling. That finding does not establish that Reddit comments cause price changes or that the indicator can reliably forecast trades. The discussion sample also represents active Reddit communities, not all retail investors.
The newer approach expands an earlier experiment. An ECB analysis published in November 2025 used around 1.8 million posts from r/wallstreetbets, applying GPT-4o to post titles. The latest work considers more communities and post text, giving researchers additional ways to compare sentiment across market topics and assets.
For market researchers and financial institutions, R-RISI may be a useful supplement to surveys and other sentiment measures, particularly when views shift quickly. The ECB publication presents it as research rather than an announced trading product or monetary policy system. The findings are the authors’ own and do not necessarily represent the ECB’s institutional views.
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