The stock market also offers a fascinating example of the laws of supply and demand at work in real-time. For every stock transaction, there must be a buyer and a seller. Because of the immutable laws of supply and demand, if there are more buyers for a specific stock than there are sellers of it, the stock price will trend up. Conversely, if there are more sellers of the stock than buyers, the price will trend down.
The bid-ask or bid-offer spread (the difference between the bid price for a stock and its ask or offer price) represents the difference between the highest price that a buyer is willing to pay or bid for a stock and the lowest price at which a seller is offering the stock.
A trade transaction occurs either when a buyer accepts the ask price or a seller takes the bid price. If buyers outnumber sellers, they may be willing to raise their bids in order to acquire the stock. Sellers will, therefore, ask higher prices for it, ratcheting the price up. If sellers outnumber buyers, they may be willing to accept lower offers for the stock, while buyers will also lower their bids, effectively forcing the price down.