For example, if an unexpectedly high earnings report comes out after the market has closed for the day, a lot of buying interest will be generated overnight, leading to an imbalance between supply and demand. When the market opens the next morning, the stock price rises in response to the increased demand from buyers. If the stock price remains above the previous day's high throughout the day, then an up gap is formed.
70680259 : why isn't COSM on the list?