In four large online experiments, we study how investors assess the relationship between stock portfolios and the market. Participants select or are randomly assigned a portfolio of stocks from a market index. They state portfolio return expectations conditional on different market outcomes, revealing implied beliefs about portfolio beta. We find general underestimation of beta which is stronger for downside beta. This asymmetry is amplified for participants who select their portfolio. They believe their portfolio goes up with the market but does not come down with it. We confirm biased beliefs about beta with financial professionals, monetary incentives, and alternative belief elicitation methods.

How do investors perceive dependence between stock returns; and how does their perception of dependence affect investments and stock prices? We show experimentally that investors understand differences in dependence, but not in terms of correlation. Participants invest as if applying a simple counting heuristic for the frequency of comovement. They diversify more when the frequency of comovement is lower even if correlation is higher due to dependence in the tails. Building on our experimental findings, we empirically analyze U.S. stock returns. We identify a robust return premium for stocks with high frequencies of comovement with the market return.

Using daily advertising data, we analyze the short-term effects of advertising on investor attention and on financial market outcomes. Based on various investor attention proxies, we show that advertising positively affects attention. However, it has only little impact on turnover and liquidity. Most importantly, short-term stock returns are not significantly influenced by advertising. Further results suggest that previous findings of an economically significant positive relation between advertising and returns are due to reverse causality. Thus, the belief that stock prices can be temporarily inflated via advertising is misguided.

We merge the literature on downside return risk and liquidity risk and introduce the concept of extreme downside liquidity (EDL) risks. The cross-section of stock returns reflects a premium if a stock’s return (liquidity) is lowest at the same time when the market liquidity (return) is lowest. This effect is not driven by linear or downside liquidity risk or extreme downside return risk and is mainly driven by more recent years. There is no premium for stocks whose liquidity is lowest when market liquidity is lowest.