Disparity in Health Insurance Claim Denials: 13% to 35%

Health insurance providers do not reject claims at a uniform rate. According to 2024 data, the largest plans available via the Affordable Care Act (ACA) marketplace exhibited denial rates for in-network claims ranging from $\text{13\%}$ to $\text{35\%}$ . Essentially, the likelihood of your medical bill being paid is heavily influenced by the specific company listed on your insurance card.

Societal Context: This data emerges amidst intense public scrutiny of the healthcare industry. Legal proceedings involving Luigi Mangione—charged with the December 2024 killing of UnitedHealthcare CEO Brian Thompson—are expected to serve as a broader referendum on a system that many perceive as prohibitively expensive and intentionally opaque.

The Statistical Landscape

On a national scale, insurers operating through the federal HealthCare.gov portal denied approximately 19% of in-network claims in 2024. This translates to roughly 85 million rejected claims in a single year.

However, the average is misleading because the variance between companies is massive. Depending on your provider, your chance of denial can fluctuate by nearly three times.

Comparison of Major Insurers

Insurer	Denial Rate	Status
Blue Cross Blue Shield of Alabama	`34.8%`	High Denial
UnitedHealth	`33.3%`	High Denial
Ambetter (Centene)	`14%`	Low Denial
Florida Blue (GuideWell)	`13%`	Low Denial

Notably, company size is not a predictor of denial frequency. While UnitedHealth is the nation's largest insurer and maintains a high denial rate, Centene and GuideWell handled tens of millions of claims while maintaining some of the lowest rejection rates in the group.

Why are Claims Denied?

There is a common misconception that insurers primarily deny claims by ~~overruling a doctor's professional opinion on medical necessity~~. In reality, the data shows a different story:

Medical Necessity: Only $\approx 5\%$ of denials were based on the care being deemed unnecessary.
Administrative Errors: Missing referrals, lack of prior authorization, or excluded services.
The "Black Box": The largest single category—36% of all denials—was labeled simply as "other".

This lack of transparency makes it nearly impossible for members or outside auditors to understand why millions of claims are being rejected.

The Appeal Cycle

The vast majority of consumers do not fight back. The process can be visualized as follows:

In 2024, fewer than 1% of denied in-network claims were appealed. Of those few who did challenge the decision, insurers upheld the original denial roughly two-thirds of the time.

Scope and Limitations of the Data

While this provides the most comprehensive public view available, it is not a total picture of the US healthcare system.

Includes: Federal HealthCare.gov marketplace plans (~16 million people).
Excludes: Employer-sponsored insurance.
Excludes: Medicare and Medicaid.
Excludes: State-run exchanges.
Note: Reporting is not fully standardized, meaning the "other" category may reflect internal bookkeeping differences.

Technical Appendix: How the Analysis Was Generated

The accompanying visuals for this report were created using an AI agent as part of the Beautiful Charts with AI series. The agent followed a specific programmatic workflow:

# Conceptual Workflow for Chart Generation
import pandas as pd
import matplotlib.pyplot as plt

# 1. Extract KFF Transparency in Coverage data
data = load_kff_denial_rates() 

# 2. Process per-insurer denial percentages
df = data.sort_values(by='denial_rate', ascending=False)

# 3. Apply "Tufte Test" design principles
# - Remove chart junk
# - Maximize data-to-ink ratio
# - Ensure high-signal labeling
generate_tufte_chart(df)

The workflow was iterated until it passed the Tufte Test, a rigorous data visualization standard developed by Goodeye Labs.

Data Source: KFF's Claims Denials and Appeals in ACA Marketplace Plans in 2024, based on federal Transparency in Coverage data.