The demand for 24-hour trading in the U.S. market is growing, but studies show that overnight trading has lower liquidity and transparency, leading to higher trading costs. Overnight trading is concentrated in large ETPs and tech stocks, which also have low costs during the day. Fewer stocks are traded overnight compared to regular trading hours. Overnight trading volume is mainly focused on ETPs and S&P 500 companies. Earnings trading is seasonal, with earnings stocks accounting for up to 20% of post-market value during earnings season. The top 15 symbols make up almost 55% of the total overnight trading value.

Read more at Nasdaq.: Concentrating on Overnight Stocks | Nasdaq