This research analyzed securities that experienced large price jumps on opening to test market efficiency. Researchers looked at price movements of over 1,500 stocks the day after a 30-100% jump. Stocks were divided into small, medium, and large groups by trading volume. Results showed stocks in the smallest volume group had the largest average price movements after opening, suggesting markets are less efficient for less actively traded stocks. The findings support the theory that a stock's competitive status in the market, as measured by volume, influences how efficiently new information is incorporated into prices.