Crowd-Out and Emergency Department Utilization.

Area of Science:

• Health economics
• Public health policy
• Healthcare utilization

Background:

• Medicaid expansion significantly alters healthcare costs and utilization patterns.
• Prior insurance status is a critical, yet often overlooked, determinant of how individuals respond to public insurance gains.

Purpose of the Study:

• To investigate how prior insurance status influences healthcare substitution patterns among newly insured individuals under Medicaid.
• To quantify the impact of losing private insurance (crowd-out) on healthcare utilization.

Main Methods:

• Utilized California's Low Income Health Program (LIHP) and Affordable Care Act (ACA) Medicaid expansions for identification.
• Employed machine learning techniques to predict prior insurance status from cross-sectional data, addressing crowd-out estimation challenges.

Main Results:

• Newly insured individuals previously uninsured experienced decreased primary care costs and increased utilization.
• Individuals who lost private insurance (crowded-out) showed reduced primary care access and increased emergency department utilization.

Conclusions:

• Prior insurance status critically shapes healthcare substitution effects following Medicaid enrollment.
• Crowd-out effects, driven by reduced primary care access, are a significant factor in increased emergency department use among the newly insured.