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Cost sharing: (g) Coinsurance (25% rate or higher) versus no cost sharing, general patient population

Healthcare: Healthcare System Efficiency
  Literature review updated November 2015.

Evaluations of health care policies and programs often measure two broad types of outcomes: (1) those that reflect the health status of people (e.g., disease incidence) and (2) those that reflect health care system costs and utilization. Cost and utilization measures may or may not be an indication of health status or well-being.

These estimates are from the RAND Health Insurance Experiment. Households were randomly assigned to different levels of cost sharing. The effect sizes reported below measure changes in medical costs, utilization, and health outcomes attributed to having a coinsurance rate of at least 25% versus free care.
 
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META-ANALYSIS
CITATIONS

*The effect size for this outcome indicates percentage change, not a standardized mean difference effect size.

Meta-analysis is a statistical method to combine the results from separate studies on a program, policy, or topic to estimate its effect on an outcome. WSIPP systematically evaluates all credible evaluations we can locate on each topic. The outcomes measured are the program impacts measured in the research literature (for example, impacts on crime or educational attainment). Treatment N represents the total number of individuals or units in the treatment group across the included studies.

An effect size (ES) is a standard metric that summarizes the degree to which a program or policy affects a measured outcome. If the effect size is positive, the outcome increases. If the effect size is negative, the outcome decreases. See Estimating Program Effects Using Effect Sizes for additional information on how we estimate effect sizes.

The effect size may be adjusted from the unadjusted effect size estimated in the meta-analysis. Historically, WSIPP adjusted effect sizes to some programs based on the methodological characteristics of the study. For programs reviewed in 2024 or later, we do not make additional adjustments, and we use the unadjusted effect size whenever we run a benefit-cost analysis.

Research shows the magnitude of effects may change over time. For those effect sizes, we estimate outcome-based adjustments, which we apply between the first time ES is estimated and the second time ES is estimated. More details about these adjustments can be found in our Technical Documentation.

Meta-Analysis of Program Effects
Outcomes measured No. of effect sizes Treatment N Effect sizes (ES) and standard errors (SE) Unadjusted effect size (random effects model)
ES SE Age ES p-value
Healthcare costs*
Percent change in total medical costs.
0 1 1137 -0.189 0.047 33 -0.189 0.001
Emergency department visits*
Whether someone visited the emergency department, or the number of times they visited the emergency department.
0 1 2296 -0.210 0.081 33 -0.210 0.010
Emergency department visits (higher-severity)*
Percent change in high-severity emergency department visits, which include visits for emergent problems such as kidney stones, cardiac arrhythmias, acute asthma exacerbations, and open head wounds.
0 1 5392 -0.230 0.059 33 -0.230 0.001
Emergency department vists (lower-severity)*
Percent change in low-severity emergency department visits, which include visits for non-emergent problems such as upper respiratory tract infections, acute bronchitis, sore throat, and low back pain.
 0 1 5392 -0.470 0.049 33 -0.470 0.001
Diastolic blood pressure
The blood pressure in the arteries when the heart rests between beats. This is the second (or bottom) number in a blood pressure reading.
 0 1 2339 0.079 0.036 33 0.079 0.027
Cholesterol
Total cholesterol (low-density lipoprotein and high-density lipoprotein).
 0 1 2262 -0.036 0.037 33 -0.036 0.327

Citations Used in the Meta-Analysis

Brook, R.H., United States., Rand Corporation., & Rand Health Insurance Experiment. (1984). The effect of coinsurance on the health of adults: Results from the Rand Health Insurance Experiment. Santa Monica, Calif: Rand.

Manning, W.G., Rand Corporation., & Rand Health Insurance Study. (1987). Health insurance and the demand for medical care: Evidence from a randomized experiment. Santa Monica, CA: Rand.

O'Grady, K.F., Manning, W.G., Newhouse, J.P., & Brook, R.H. (1985). The impact of cost sharing on emergency department use. Santa Monica, CA: Rand Corporation.