Usually, the supply curve of any good is constantly shifting. The two main reasons why a supply curve will shift is if there is a change in the number of sellers, and if the cost of production increases or decreases.

An example of a product that experienced a change in the supply curve is gourmet cheeseburgers (i.e. from Five Guys, Shake Shack, Applebees). Twenty years ago, places, where these types of burgers could be purchased, were largely limited to restaurants. Over time, however, the market evolved, and this food became available in most of a "faster food" type of market. As places like Five Guys and Shake Shack have become more popular, the number of sellers in the market for cheeseburgers has steadily increased. This increase has caused the market supply curve to increase, that is, shift to the right, because there were now more units supplied at any given price.