The urge to merge is sweeping managed health care. Aetna announced Friday a $37 billion deal to acquire Humana. Anthem and Cigna are in merger talks and could be next. The national for-profit insurers are on an anxious mission to consolidate. These combinations will sharply reduce competition and consumer choice, as five big insurers shrink, probably, to three.

This trend is a direct consequence of ObamaCare, reflecting the naïveté of its architects and the fulfillment of their myopic vision. For Aetna, the deal is aimed...