The list cites 11 sources:
– 1Barber, Lee, Odean (2010): Do Day Traders Rationally Learn About Their Ability?
– 2Odean (1998): Volume, volatility, price, and profit when all traders are above average
– 3Barber, & Odean (2000): Trading is hazardous to your wealth: The common stock investment performance of individual investors
– 4 Kumar: Who Gambles In The Stock Market?
– 5 Barber, Odean (2001): Boys will be boys: Gender, overconfidence, and common stock investment
– 6Calvet, L. E., Campbell, J., & Sodini P. (2009). Fight or flight? Portfolio rebalancing by individual investors.
–7Barber, B. M., Lee, Y., Liu, Y., & Odean, T. (2009). Just how much do individual investors lose by trading?
– 8Gao, X., & Lin, T. (2011). Do individual investors trade stocks as gambling? Evidence from repeated natural experiments
– 9Strahilevitz, M., Odean, T., & Barber, B. (2011). Once burned, twice shy: How naïve learning, counterfactuals, and regret affect the repurchase of stocks previously sol.
– 10Da, Z., Engelberg, J., & Gao, P. (2011). In search of attention
– 11De, S., Gondhi, N. R. & Pochiraju, B. (2010). Does sign matter more than size? An investigation into the source of investor overconfidence
However, as with all statistics, it depends on what you measure, how you measure and how you aggregate. Ie. there's a world of difference buying mutual funds, and being an active trader, which is in #4 in the list. It makes perfect logical sense why most active traders win less / lose more than buy & hold investors, and matches reality of most who try. What I see however, is that people never brag about their losses, but once in a while, a huge winner stands out and become glorified, among all the unspoken invisible loser trades. The latest being latest crop of BTC winners, having 2x-5x-10x winnings. So there's a feedback loop of wrong impressions, and of crushed dreams and hopes and wishes. Worst of it all is the hope though, because it is false and non-repeatable for most.
So what I'm saying is one should only do trading and research on such if that is what one love / like to do, it doesn't upset your life and one can have a good balance with it. Most may do better becoming investors though, as successrate is clearly higher.