Spatial Accessibility and Health-System Concentration of Reachable Hospital Capacity in New Jersey
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Background
Spatial accessibility measures estimate how much hospital capacity a community can reach but do not show how that capacity is distributed across health systems. A community may have several reachable hospitals but still depend on one or a few systems.
Methods
We used the enhanced two-step floating catchment area method to estimate staffed-bed spatial accessibility for New Jersey census tracts. We included short-term acute care hospitals in New Jersey and neighboring states within a 30-minute drive of at least one New Jersey tract. For each tract, we grouped hospital-level accessibility contributions by health system and calculated a Herfindahl–Hirschman Index (HHI). Spearman correlations examined associations of E2SFCA and HHI with tract-level sociodemographic characteristics.
Results
Of 163 reachable hospitals, 94 were outside New Jersey and supplied 62.7% of reachable staffed beds. Across 2,172 tracts, the mean E2SFCA score was 1.98 beds per 1,000 distance-weighted residents; among 2,161 tracts with positive scores, the median HHI was 0.31. Using cutoffs of E2SFCA <2.0 and HHI ≥0.18, 934 tracts met both criteria, while an E2SFCA-only rule missed 655 tracts with higher accessibility but high concentration. E2SFCA and HHI correlations had opposite signs for seven of eight sociodemographic characteristics.
Conclusions
E2SFCA and HHI classified New Jersey tracts differently under the illustrative cutoffs. Contribution-based HHI identifies tracts in which a closure, service relocation, or capacity reduction involving a major contributing system could affect a large share of modeled accessible capacity.
