There is a metric that most marketers have heard of in passing but surprisingly few use regularly. The Brand Development Index, or BDI, tells you something simple and profoundly useful: how your brand performs in a specific market segment compared to how it performs everywhere else.
I started paying real attention to BDI when I was working on a campaign for a regional brand that assumed it was strongest in its home market. The BDI numbers told a different story. The brand was actually overperforming in three secondary markets and underperforming at home. That single data point changed the entire media plan.
The Brand Development Index (BDI) is a quantitative measure that compares a brand's sales performance in a specific market segment (usually a geographic area, but it can be a demographic group) against the brand's average performance across all markets. It was developed for media planning and has been a staple of CPG marketing for decades.
The Marketing Accountability Standards Board (MASB) includes BDI in its common language marketing dictionary, defining it as the metric that "relates the percent of a brand's sales in a market to the percent of the population in that same market."
NielsenIQ's CPG Dictionary defines it similarly, emphasizing its role in identifying geographic strengths and weaknesses for brand distribution and promotion decisions.
The BDI calculation is straightforward:
BDI = (% of Brand's Total Sales in Market X / % of Total Population in Market X) x 100
Or expressed differently:
BDI = ( (Brand Sales in Segment / Total Brand Sales) / (Population in Segment / Total Population) ) x 100
A BDI of 100 means your brand performs at parity with the market. Your share of sales in that segment matches that segment's share of the total population. Above 100 means overperformance. Below 100 means underperformance.
Say you sell protein bars nationally, and you want to evaluate performance in the Miami DMA (Designated Market Area).
| Data Point | Value |
|---|---|
| Your brand's total U.S. sales | $50 million |
| Your brand's sales in Miami DMA | $4 million |
| Total U.S. population | 330 million |
| Miami DMA population | 6.1 million |
| % of brand sales in Miami | 8.0% |
| % of U.S. population in Miami | 1.85% |
| BDI | 432 |
A BDI of 432 means your brand sells at 4.3x the rate you would expect based on population alone. Miami loves your protein bars. This is the kind of insight that changes how you allocate your advertising reach and advertising frequency budgets.
BDI becomes much more powerful when paired with the Category Development Index (CDI). CDI measures the same thing, but for the entire product category rather than your specific brand.
CDI = (% of Category's Total Sales in Market X / % of Total Population in Market X) x 100
The BDI/CDI matrix creates four strategic quadrants: