Your best-performing market on paper might be your weakest bet on the ground. Most media plans can’t tell the difference, and that blind spot is costing brands their next round of growth. 

The instinct runs deep: build the plan around the largest cities and the regions with the most existing customers. It feels like the safe, defensible choice. It’s also, more often than not, the wrong one. Money goes where the volume already is, and you can see the pattern across marketing. eMarketer projects that by 2028, Amazon’s retail media revenue will exceed $75 billion, more than $65 billion ahead of the next-largest network. 

Category development index (CDI) and brand development index (BDI) correct for that bias. Together, they show which markets are big and which ones have room to grow. This blog covers how to calculate both indices, how to read them together, and how to turn the results into a market prioritization strategy your media plan can follow. 

What do CDI and BDI Measure? 

CDI measures how heavily a market buys for your product category, relative to its share of the population. BDI measures the same thing for your brand. Both use the same formula: 

• CDI = (category sales in a market ÷ total category population in that market) ÷ (total category sales ÷ total population) × 100
• BDI = (brand sales in a market ÷ population in that market) ÷ (total brand sales ÷ total population) × 100

A score of 100 means a market buys exactly its population-based share. A score above 100 means the market over-indexes, and a score below 100 means it under-indexes. For example, a metro with 4% of the U.S. population and 6% of category sales has a CDI of 150. Its residents buy the category at 1.5 times the national per-capita rate.

The population adjustment is what makes the framework useful. The indices compare each market with national per-capita sales, not total volume. That lets a midsize market with heavy demand outrank a major metro with average demand, even when the metro moves more dollars.

Two rules to keep your math honest. First, match the population figure to your actual buyer. If you sell to households, parents, or adults 25-54, use that count instead of total residents. Second, keep every input consistent, with the same time period, the same unit of measure, and the same market definitions across brand, category, and population data.

Reading CDI and BDI Together 

CDI shows how much demand exists in a market. BDI shows how much of that demand your brand captures. Either number alone can mislead you. A strong BDI can look like a win until you realize the category barely exists. A strong CDI looks like an opening until you find out a competitor has owned the market for a decade.

Dividing BDI by CDI gives you a fast read on headroom. The result compares your brand’s share in that market with its national share. A ratio of 1.0 means your share there matches your national average. A ratio of 0.5 means you’re capturing half your usual share, and that gap is the opportunity.

Why Are “Biggest” and “Best” Different Questions? 

Raw sales rank markets by size, not by potential. A top-five market can lead every dashboard and still return less growth per dollar than a market half its size.

High index scores deserve scrutiny, too. When both CDI and BDI sit well above 100, your brand may already have most of the available demand, so each added dollar buys less. 

Most planners already know their underfunded markets. The problem is that budget reviews rarely ask for that information. Quarterly reporting ranks markets by total sales, so a smaller market with strong demand and thin brand share looks like a low priority every time the numbers come up. It gets funded last, not because anyone decided it wasn’t worth the money, but because nothing in the report made the case. A CDI/BDI matrix makes that case with numbers attached.

What 4 Market Types Does the CDI/BDI Matrix Reveal? 

Plot each market on a grid, with 100 as the dividing line on both axes. Each quadrant calls for a different approach to media budget allocation.

What Does an Example of a CDI/BDI Matrix Look Like? 

Consider a hypothetical brand with $50 million in annual sales across 4 markets: 

Market A looks like the obvious priority. It produces $7 million in brand sales, and the brand holds 17% more share there than it does nationally. Spending more in Market A protects a strong position, but it won’t produce much new growth.

Market B ranks third in brand sales at $1.5 million, and most plans would treat it as an afterthought. Yet its residents buy the category at 1.5 times the national rate, and the brand captures only half its usual share. If the brand reached its national-average share there, Market B sales would double to $3 million. That’s $1.5 million in new revenue from a market that would normally get funded last.

Market C shows the limits of a strong BDI. The brand performs well there, but thin category demand restricts how far it can grow. 

Market D is weak on both counts. Category demand runs below the national rate, and the brand captures only three-quarters of its usual share. Closing that gap entirely would add about $300,000 in sales, a fifth of Market B’s upside, so it’s a natural candidate to deprioritize. Before cutting, though, check two things: whether the low BDI comes from thin distribution rather than weak demand, and whether category sales there are rising or falling. A low/low market with growing category demand may deserve a small test budget instead of an exit.

How Do You Build a CDI/BDI Matrix for Your Own Markets? 

Start with three data sets. Pull brand sales by market from internal reporting. Get category sales from a syndicated source such as Circana or NielsenIQ, or from trade association data. Take target-buyer population counts from the U.S. Census Bureau.

Calculate CDI, BDI, and the BDI/CDI ratio for every market, then plot each market and assign its quadrant.

Finally, add a trend line. CDI and BDI capture a single moment and say nothing about direction. Calculating both for the past two or three years shows whether each category is growing, flat, or shrinking. A low-CDI market with rising category demand calls for a very different plan than one in decline.

How to Turn Your CDI/BDI Matrix Into a Budget? 

A matrix only matters if it changes where the money goes. Four practices make that happen. 

• Segment at the right level. Work at the metro or DMA level, matched to how you buy media. Regional averages hide the gaps this analysis is meant to find. Refresh the matrix at least once a year.
• Choose a strategy and assign a weight. In growth mode, rank high-CDI markets first and sort them by the lowest BDI/CDI ratio. In share-defense mode, rank by BDI and protect the markets where your share runs highest. Write the choice down so the team plans against the same goal.
• Rule out distribution problems. A market can post a low BDI simply because the product isn’t on shelves or isn’t stocked consistently. That calls for a sales and trade fix, not a media cut. Check distribution data before you pull budget from any low-BDI market.
• Audit the plan every quarter. Compare actual spend by market with the plan, and review targeting and location settings on every platform. Automation drifts, as the next section explains.

How Does Platform Targeting Affect Your CDI/BDI Strategy? 

A CDI/BDI-driven plan is only as strong as your ability to enforce it once the budget hits the platforms where you actually spend.

In March 2026, Google changed how lookalike segments work in Demand Gen campaigns. Similarity tiers used to act as hard limits. They now act as signals, and Google’s AI can extend reach past the selected tier when it predicts better conversion rates or a lower cost per action. 

Lookalikes govern audiences rather than geography, but the risk carries over. Algorithms look for the cheapest conversions, and usually come from markets where your brand already performs well. Those are often the high-BDI markets your plan intends to hold steady. 

Geographic settings need the same attention. Google Ads location targeting defaults to people who are in or have shown interest in your chosen locations. Switching to “Presence” keeps spend inside your target markets. Budget structure matters as well. A single national campaign lets the algorithm decide allocation, while separate campaigns or budgets by market tier keep that decision with your team.

Put the Budget Where the Growth Is 

Every brand has a Market B. It’s the market where demand is strong, your share is thin, and the budget stays small because the market has never looked important. CDI/BDI analysis finds that market and sizes what it’s worth, which gives you the evidence to fund it.

The analysis depends on clean inputs. If sales reporting is inconsistent or attribution is broken, the matrix will point to the wrong markets, and it will look convincing while it does. Get the data right first, and the rest of the plan follows.

Techint Labs helps brands build CDI/BDI matrices from verified sales and attribution data, then carry the findings into their media plans. Book a market analysis to find the markets your budget is missing.