The market for a given product or service known as the "market potential" or the "total addressable market (TAM)." Given that this is the market to be segmented, the market analyst should begin by identifying the size of the potential market. For existing products and services, estimating the size and value of the market potential is relatively straightforward. However, estimating the market potential can be very challenging when a product or service is totally new to the market and no historical data on which to base forecasts exists.