The par value has practically no effect on the market value of a stock. The market determines how much a stock is worth based on a variety of factors, but par value isn’t one of them.
How investors use par value
Par value is commonly used to determine the price an investor is willing to pay for a bond.
The key factor in determining the value of the bond is yield to maturity. Yield to maturity determines how much an investor will earn in coupon payments and capital gains by buying and holding a bond to its maturity date. Those are both determined by its par value and coupon rate. The market will price similar bonds so that they all produce the same yield to maturity.
For example, let’s imagine a company that’s issuing debt to raise capital. It issues a two-year bond with a 5% annual coupon rate. A year later, market rates have increased, and it issues a one-year bond with a 6% annual coupon rate.
Investors aren’t going to pay par value for that original two-year bond (maturing in one year) when they can get a substantially similar bond with a higher coupon rate. Instead, they will pay a price lower than par value, such that it effectively yields 6%.
They can determine that price with simple algebra. In this example, the two-year bond holder will receive par value plus 5% at maturity. The one-year bond holder will receive par value plus 6%. So they divide the older issue’s payment in one year by the new issue’s, 1.05 divided by 1.06. That equals about 99%, which is the percentage of par value investors should be willing to pay for the older issue.