What it is:
How it works/Example:
Note that the number of shares wanted (the bid size) and the number of shares offered for sale (the ask size) may be different. This means that an investor may only be able to purchase 5,000 of a desired 10,000 Company XYZ shares at $51.50 if there are only 5,000 shares for sale at that price.
Why it matters:
It is important to remember one key aspect of bid and ask prices: purchasers pay the ask price and sellers receive the bid price. This is how securities dealers make a profit: Their job is to buy stocks at the ask price and sell at the bid price. Thus, the amount of price tension is proportional to the size of the dealer's profit (although other fees are part of the bid-ask spread too).
Many traders and analysts scrutinize price tension to understand what prices trigger demand for both sellers and buyers. Other traders and analysts feel that price tension itself has little predictive value.