Market segmentation index is a way to measure how much of a market is divided into small groups of people. Let's say you are making a new kind of cereal. You want to know what kind of cereal people like so that you can make something that people will want to buy.
To figure out what kind of cereal people like, you can measure the market segmentation index. That means you are looking at all the different kinds of cereal people buy and figuring out how many different groups like each type.
For example, you might find that 20% of people prefer crunchy cereal, 10% prefer sweet cereal, and 70% prefer a combination of sweet and crunchy cereal. That tells you that most people prefer the combination, so you could make a cereal that is a mix of both sweet and crunchy.
By measuring the market segmentation index, businesses can make sure they make products that people will want to buy.