Patients assigned to different primary care providers in the US have different levels of spending. This is not surprising, but to what degree is this result driven by variation in health care utilization compared to prices? A paper by Mehrotra et al. (2023) aims to answer this question using 2018 claims data from a large commercial insurer. They find that:
Per-patient spending in the highest quartile of spending medical groups was $1813 higher than per-patient spending in the lowest spending quartile of medical groups (50% higher relative spending). This overall difference was primarily driven by differences in inpatient care, imaging, and specialty care. In the scenario where we used standardized prices, the difference in spending between medical groups in the top and bottom quartiles decreased to $1425, implying that 79% of the $1813 difference in spending between the top and bottom quartile groups is explained by utilization and the remaining 21% by prices. The likely explanation for the modest impact of prices is that patients cared for by a given medical group receive care across a wide range of providers.
In short, utilization is driving nearly 80% of the differences in health care cost among commercially insured individuals in the U.S. You can see some older data from KFF for Medicare beneficiaries here as well.