DDVADaVita Inc.

DaVita runs dialysis centres — a procedure without which a patient with failed kidneys does not live.

The patient comes three times a week for several hours, for years, and chooses a centre by proximity to home. The flow is predictable down to the individual, and demand depends on neither the economy nor the season — one of the most durable models in medicine.

The economics come down to who pays: the government programme covers treatment for nearly everyone but reimburses at a rate that barely covers costs, while private insurance pays several times more. The company's profit effectively arises from a small share of commercially insured patients. Risks: reimbursement changes, staffing costs and the shift to home dialysis. The company pays no dividend but buys back stock very actively.