The study looked at how trading overnight affects how prices are determined during the day in the Korean stock index futures market. They used data from January 2009 to March 2011 and found that trading overnight helps set prices faster and more accurately during the day. About a quarter of the day's price discovery happens overnight, where traders use both private and public information to make decisions. This shows that futures trading is important for figuring out the value of the cash index, especially when the cash market is closed.