<mods:mods xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-8.xsd"><mods:titleInfo><mods:title>From Payer to Provider: Impacts of Insurer Vertical Expansion into Physician Services</mods:title></mods:titleInfo><mods:typeOfResource authority="primo">technical_reports</mods:typeOfResource><mods:abstract>Vertical integration can both create efficiencies and harm competition. We examine these tensions through one of the most prominent forms of vertical integration in the United States: the acquisition of physician practices by the nation’s largest insurer, UnitedHealth Group. Using a difference-in-differences design and Medicare administrative data, we find minimal changes to acquired practice case mix or care quality, but do find evidence of increased coding intensity. Insurer-provider integration can have significant fiscal externalities.</mods:abstract><mods:name><mods:namePart>Jeffrey Marr</mods:namePart><mods:role><mods:roleTerm authority="marcrelator" authorityURI="http://id.loc.gov/vocabulary/relators" valueURI="http://id.loc.gov/vocabulary/relators/aut">Author</mods:roleTerm></mods:role></mods:name><mods:name><mods:namePart>Christopher M. Whaley</mods:namePart><mods:role><mods:roleTerm authority="marcrelator" authorityURI="http://id.loc.gov/vocabulary/relators" valueURI="http://id.loc.gov/vocabulary/relators/aut">Author</mods:roleTerm></mods:role></mods:name><mods:name><mods:namePart>Xiaoxi Zhao</mods:namePart><mods:role><mods:roleTerm authority="marcrelator" authorityURI="http://id.loc.gov/vocabulary/relators" valueURI="http://id.loc.gov/vocabulary/relators/aut">Author</mods:roleTerm></mods:role></mods:name><mods:originInfo><mods:dateCreated>2026-04-14</mods:dateCreated></mods:originInfo><mods:subject authority="local"><mods:topic>Primary Care</mods:topic></mods:subject><mods:subject authority="local"><mods:topic>Insurer vertical integration</mods:topic></mods:subject><mods:subject authority="local"><mods:topic>health care markets</mods:topic></mods:subject><mods:subject authority="local"><mods:topic>United Healthcare</mods:topic></mods:subject><mods:genre>Working Paper</mods:genre><mods:accessCondition type="use and reproduction">All rights reserved</mods:accessCondition><mods:accessCondition type="rights statement" xlink:href="http://rightsstatements.org/vocab/InC/1.0/">In Copyright</mods:accessCondition><mods:accessCondition type="restriction on access">All Rights Reserved</mods:accessCondition><mods:identifier type="doi">10.26300/9xte-nh94</mods:identifier></mods:mods>