Cardiovascular Access · U.S. Counties · Geometric Centroids
Drive Time to Nearest PCI-Capable Hospital — Geometric Centroids
Distance measured from the geometric centroid of each county — the mathematical
midpoint of its land area. For large, irregularly shaped counties in the West, this point often
falls in unpopulated desert or forest, overstating the true distance to care.
Compare with the population-weighted centroid map to see the difference.
<30 min15.1% of counties
30–90 min57.1% of counties
>90 min27.8% of counties
28%
of counties appear beyond 90 min using geometric centroids
72%
of counties within 90 min (geometric centroid measure)
1,248
hospitals billing Medicare PCI (DRG 246–251) geocoded via ZIP
5.3%
of population actually beyond 90 min even with geometric centroids
Why This Map Is Wrong — and That's the Point
Geometric centroids measure from the middle of the land, not where people live.
For compact eastern counties this barely matters. For sprawling western counties it creates
dramatic distortions. Washoe County (Reno, NV) has two PCI hospitals, but its geometric centroid
sits 47 miles away in the northern Nevada desert. San Bernardino County's midpoint
is in the Mojave — 52 miles from Loma Linda, which is 6 miles from the population center.
This map uses the naive approach to show why the population-weighted centroid map is the
methodologically correct one.