  We study the investor beliefs, sentiment and disagreement, about stock market
returns during the COVID-19 pandemic using a large number of messages of
investors on a social media investing platform, \textit{StockTwits}. The rich
and multimodal features of StockTwits data allow us to explore the evolution of
sentiment and disagreement within and across investors, sectors, and even
industries. We find that the sentiment (disagreement) has a sharp decrease
(increase) across all investors with any investment philosophy, horizon, and
experience between February 19, 2020, and March 23, 2020, where a historical
market high followed by a record drop. Surprisingly, these measures have a
sharp reverse toward the end of March. However, the performance of these
measures across various sectors is heterogeneous. Financial and healthcare
sectors are the most pessimistic and optimistic divisions, respectively.
