Historically, when does the market tend to show the largest upward bias?

The market historically tends to show the largest upward bias in the last 15 minutes before closing. This phenomenon is largely attributed to various factors, including the behavior of institutional investors and end-of-day trading strategies. Many traders and fund managers adjust their positions towards the end of the trading session to align with their daily targets or to respond to news developments that occurred throughout the day.

As the market approaches the close, buying pressure can increase, particularly from institutional entities who often engage in window dressing, which involves buying certain stocks to improve the appearance of their portfolios. This activity creates upward pressure on stock prices, leading to a notable bias toward gains during this period.

In contrast, during the market's opening, fluctuations can be more erratic as traders react swiftly to overnight news; the lunch hour tends to see lower trading volume and less volatility; and the midday trading session can often be quieter, with less pronounced movements in price. Therefore, the time immediately before market close stands out as the period with the most significant upward bias.