The overlap, by drive time
Both footprints routed on the road network. “Both” is the population that can reach a Costco and a BJ's Wholesale Club within the same drive time.
| Drive time | Costco reach | BJ's Wholesale Club reach | Both | % of Costco | % of BJ's Wholesale Club |
|---|---|---|---|---|---|
| 5 min | 11,431,545 | 6,278,444 | 296,171 | 2.59% | 4.72% |
| 10 min | 67,195,045 | 30,463,460 | 8,936,714 | 13.3% | 29.34% |
| 15 min | 132,582,198 | 56,412,403 | 31,768,776 | 23.96% | 56.32% |
| 30 min | 214,293,032 | 102,440,372 | 83,934,789 | 39.17% | 81.94% |
| 60 min | 263,797,508 | 132,166,388 | 119,879,002 | 45.44% | 90.7% |
What it means
At 30 minutes, 39.17% of the people Costco can reach are also inside a BJ's Wholesale Club catchment. 130,358,243 people are Costco's alone.
A high shared percentage is not automatically bad. It means the two chains have solved the same geography. It matters when one of them is planning to add units: incremental reach comes from the exclusive population, not the shared one.
Narrative Geo does not sample. Every trade area is routed on the actual road network with OSRM, against full Census/ACS population and a maintained POI set. The drive-time matrix is precomputed at 1.08 billion rows, so a national query across a 20,000-store chain returns in seconds rather than being metered per location.