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. 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. ==Construction==