The brand development index or BDI quantifies how well a brand performs in a market, compared with its average performance among all markets.[1] That is, it measures the relative sales strength of a brand within a specific market (e.g., the Pepsi brand among 10–50-year-olds).[2]
The purpose of the BDI metric is to quantify the relative performance of a brand within specified customer groups. The index helps marketers identify strong and weak segments (usually demographic or geographic) for individual brands.[1]
The BDI is especially useful in conjunction with the category development index (CDI). It can be used in deciding the allocations in the media to which a specific brand is advertised. It can also be used to determine how much advertising, or promotion effort is, or should be put in that specific market.
BDI: An index of how well a brand performs within a given market group, relative to its performance in the market as a whole.[1]
For example, one might hypothesize that sales per capita of Ben & Jerry's brand ice cream would be greater in the brand's home state, Vermont, than in the rest of the country. By calculating Ben & Jerry's BDIs for Vermont and for the rest of the country, marketers could test this hypothesis quantitatively.
Govoni also defined the BDI as the index of brand sales to category sales,[3] though this ratio is more commonly referred to as market share.
