For example, a 2004 study by Brad Barber and Terrance Odean of the University of California and Yi-Tsung Lee and Yiu-Jane Liu at National Chengchi University acquired trade-by-trade data on individual day traders on the Taiwan Stock Exchange. The study found that only the top 1% of day traders made a profit – after deducting trading costs – in two consecutive six-month periods, and the median profit was hardly worth the effort: only about US$4000.