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Mexico Seguro Popular — Health Insurance Coverage Expansion

Harvard School of Public Health / Mexican Ministry of Health · Mexico · 2002

Summary

The Seguro Popular evaluation used a randomized cluster design — rare in large-scale health insurance research — to test whether extending insurance to uninsured Mexican households reduced catastrophic medical expenditures. It did: the 23% reduction in households facing ruinous health costs was meaningful and real. But like the Oregon Medicaid experiment in the United States, the study found limited evidence of short-term health outcome improvements, which critics seized on to question the value of coverage expansion. The more accurate interpretation is that financial protection is independently valuable — families not bankrupted by illness invest more in education, savings, and children's health — and that chronic disease outcomes require longer observation windows than two-year evaluations can provide. The study is a useful case study in interpreting evaluation findings in politically contested domains.

Research question

"Does expanding health insurance to uninsured low-income households reduce catastrophic health expenditures and improve utilization of preventive care?"

Methodology

Intervention

Seguro Popular launched in 2002, offering free or subsidized health insurance to households not covered by social security. Rollout was phased by municipality due to administrative capacity constraints. Researchers used the phased rollout as a natural experiment, comparing early-rollout to late-rollout municipalities in a matched design.

Assignment

Randomized paired-cluster design; 100 matched pairs of municipality clusters (50 treatment, 50 control) randomly assigned to early vs. delayed rollout; 32,000 households surveyed

Sample size

32,000 households across 100 municipality cluster pairs

Primary outcome

Catastrophic health expenditure (out-of-pocket spending exceeding 30% of income); utilization of outpatient care; coverage rates

Effect estimate

Catastrophic health expenditure: −23% reduction in treatment municipalities at 10 months; coverage rates rose substantially; outpatient care utilization increased; no significant effect found on mortality or child health in the short follow-up window — consistent with Mexico Oregon Medicaid parallels

Decision

Seguro Popular expanded to cover 52 million Mexicans by 2012, making it one of the largest health coverage expansions in Latin American history; replaced by IMSS-Bienestar in 2020; study widely cited in global health financing literature as evidence for coverage expansion reducing financial risk even when health outcomes are harder to detect at short follow-up

Result

Mixed

Catastrophic health expenditure: −23% reduction in treatment municipalities at 10 months; coverage rates rose substantially; outpatient care utilization increased; no significant effect found on mortality or child health in the short follow-up window — consistent with Mexico Oregon Medicaid parallels

Evidence strength

Limited

Observational or pre-post design; correlation not necessarily causal.

Replication status

Partially replicated

Institution

Harvard School of Public Health / Mexican Ministry of Health

Location

Mexico

Year

2002

Policy area

Public Health

Mechanism

Information

More from these institutions

Other trials of this mechanism

Cite this entry

Harvard School of Public Health / Mexican Ministry of Health. (2002). Mexico Seguro Popular — Health Insurance Coverage Expansion. The Experiment Society Registry. Retrieved from https://www.experimentsociety.org/registry/mexico-seguro-popular (primary report: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(09)60537-6/fulltext)

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