BDI and CDI compare a sales share with a population share on a base of 100.
BDI and CDI compare a sales share with a population share on a base of 100. They reveal a relative gap between brand, category and market. MRI and BAS do not denote one recognised formula: numerator, denominator, period and weights must be supplied before any calculation or comparison.
Decision and method.
Calculate BDI and CDI with coherent units, then refuse any MRI or BAS whose convention is not explicitly documented. Define market, brand and category by area, period, unit and source; population share uses the same scope as sales. Calculate BDI = brand sales share / population share × 100; CDI = category sales share / population share × 100. Read them together as a configuration, not proof of whether distribution, price, demand or competition creates the gap. For MRI or BAS, record formula, weights, data, missing-data treatment, base, frequency and owner. Display source shares with the index and treat missing data as unavailable, never zero.
Worked example.
In an illustrative case, an area represents 10% of population, 8% of brand sales and 12% of category sales. BDI = 8 / 10 × 100 = 80. CDI = 12 / 10 × 100 = 120. The contrast deserves investigation into availability, preference, price and competition; it proves neither causal potential nor optimal allocation. An index of 120 means 20% above the defined base, not absolute performance or causality.
Checks and limits.
Use the same area, period and unit in numerator and denominator; show source shares; refuse MRI or BAS without formula, base, source and explicit weighting. BDI/CDI are descriptive and sensitive to market and population definition; base 100 is neither universal goal nor automatic investment threshold; MRI/BAS can be incomparable company or supplier conventions; these indices replace neither incremental analysis nor financial brand measurement.
Resources and sources.
Download the index grid. Related: brand measurement and economics, KPI architecture, qualify evidence. Sources: Nielsen market-development indices; Farris et al., Marketing Metrics.