Jón Guðjónsson
Fundamental versus Short-Term Trading:
Investor Composition and Herding
This paper investigates whether fundamentally oriented investors reduce herding in financial markets. Using a novel implementation of the structural sequential trading model of Cipriani and Guarino (2014), we obtain per-trade herding estimates that allow us to identify distinct herding episodes. We apply this methodology to proprietary transaction-level data from the Icelandic stock market, linked to trader identities. Our results reveal clear asymmetries between investor types. Buy herding is driven by individual investors, while institutional investors trade against the herd. By contrast, sell herding is driven by institutional investors when individual participation is weak. Thus, when less fundamentally oriented individual investors are less pronounced in the market, differences in horizons and strategies within the institutional sector start to matter, and the less fundamentally oriented subset of institutional investors can itself become the driver of herding.
Jón Guðjónsson is a doctoral student in the Department of Economics at CBS in Copenhagen. His research focuses on macroprudential policy, financial stability, and theoretical macroeconomics. He has also worked on the implementation of macroprudential policy since 2017, first at the Financial Supervisory Authority and later in the Financial Stability Department of the Central Bank of Iceland.
