Retail investors’ trading and stock market liquidity

•Higher retail investors’ trading contributes to aggregate stock market liquidity.•Retail investors’ characteristics affects their trading activity.•Retail investors’ trading does not create price noise at the aggregate market level.•The evidence suggests that retail investors contribute to market quality. The paper investigates the relation between retail investors’ participation in trading and aggregate stock market liquidity. The findings show a positive and significant relation between retail investors’ trading and stock market liquidity. Examination of the determinants of retail investors’ trading reveals that, on average, retail investors with more diversified trading activity tend to trade when liquidity is higher, the frequency of their arrival to the market is not affected by the level of liquidity, and retail investors are willing to trade at a lower liquidity level as sellers than as buyers. Moreover, retail investors’ trading does not create price noise at the aggregate market level. Overall, the evidence suggests that retail investors contribute to market quality.