I am a PhD candidate in finance at the University of St. Gallen and the Swiss Finance Institute.

My research studies how financial intermediaries and platforms shape investor behaviour and market outcomes. My job market paper examines how YouTube finfluencers affect retail investor trading. In other work, I study competition and strategic price setting in the mutual fund industry.

I like to study economically important questions by applying network analysis, natural language processing, and other data-driven approaches to financial markets.

Prior to my doctoral studies, I worked as a Quantitative Analyst at Morningstar Sustainalytics. I hold a master's degree in finance from Queen's University and bachelor's degrees from Brock University and Dublin City University.

Email: aaronjames.black@unisg.ch

Working Papers

YouTube Finfluencers and Retail Investor Stock Trading

Abstract: I study stock-investing finfluencers on YouTube, the most popular social-media platform for retail-investor information. I use a large language model to extract stock mentions and stances (bullish, neutral, bearish) from video transcripts. Finfluencers cover high-attention stocks with extreme recent absolute returns. Their stock picks exhibit modest short-run returns, but do not generate abnormal performance over longer horizons. Using TAQ-based retail trading measures at half-hour frequency and within-day variation in video publication timing, I show that retail trading increases following a stock mention. One hour after publication, retail buys are about 3.4% higher than for stocks mentioned later in the day. These findings suggest that finfluencers are important retail-facing market intermediaries that allocate investor attention and induce trading activity.

Pricing Differentiated Funds: The Puzzle of ESG Fund Fees (with Julian F. Kölbel)

Sustainable and Impact Investments International Conference - MCC Best Paper Award 2025 (Second Place)

Abstract: We document a robust anomaly in the fee setting of U.S. mutual funds: ESG funds charge net expense ratios 11.5 basis points lower than those of conventional funds across providers, and 6.5 basis points lower within provider. Using panel data from 2011-2024, we show this fee gap persists across data sources, ESG classifications, and market segments. A Hotelling-style model of horizontal differentiation predicts that funds with higher returns and stronger differentiation should command higher fees. ESG funds have outperformed peers net-of-fees and exhibit greater textual differentiation, but nonetheless charge lower fees. The result is inconsistent with standard theories of fee setting based on performance signals or competitive differentiation.