Methodology & Data Sources

Data Sources

• NAIC MCAS 2024 (Market Conduct Annual Statement): Complaint ratios, total complaints, and justified complaint counts for 215 insurers across all 50 states + DC, from the National Association of Insurance Commissioners. This is the authoritative industry source for insurance company complaint data.
• CMS Transparency in Coverage PUF PY2026: Claim denial rates published by the Centers for Medicare & Medicaid Services under the ACA Transparency in Coverage rule. Covers 145 health insurance issuers reporting for plan year 2026, published as the plan-year 2026 Transparency in Coverage PUF alongside the rest of the data.healthcare.gov marketplace files. A further 24 issuers last reported in the previous plan year and are retained on their own pages, dated to that year, because the current federal file no longer covers them. Illinois moved to a state-based marketplace for 2026, so its carriers left the federal file.
• CMS Medicare Advantage Analysis: Prior authorization request, denial, and appeal rates from the CMS Office of Inspector General report OEI-09-22-00380 and KFF 2023 Medicare Advantage analysis. See also Medicare.gov.
• NAIC 2023 Auto Insurance Database Average Premium Supplement: State-level average auto insurance premiums and expenditures (2019-2023), from the National Association of Insurance Commissioners. Powers the auto-rates and state-cost pages.
• NAIC 2024 Property/Casualty Market Share Report: Private-passenger-auto group rankings by direct written premium, with NAIC group codes. Powers the auto market-share pages; it is a separate 2024 source, not the state-expenditure series above.

Coverage

PlainInsurer covers 215 insurance companies across all major insurance lines, homeowners, auto, life, and health. Not all companies have data for all four sources; grades are calculated from whichever datasets are available for each insurer.

Grade Calculation

Grades are computed from a composite score with three components:

1. Complaint ratio score (primary, all insurers): NAIC complaint ratio compared to the industry median. A complaint ratio of 1.0 is average; above 1.0 means more complaints than expected relative to market share. Ratios significantly above median lower the grade.
2. Claim denial rate (health insurers only): CMS Transparency in Coverage claim denial rate compared to the health insurance industry median
3. Prior authorization denial rate (Medicare Advantage only): Rate of prior authorization denials compared to peer plans

The composite score maps to letter grades (A through F) using a bell-curve distribution relative to the full insurer population, so grades reflect relative standing rather than absolute thresholds.

Multi-vintage disclosure (cross-stage population coupling): the three components do not share one fiscal year. Complaint ratios come from the retained NAIC MCAS extract (currently the 2024 complaint-index release); marketplace claim-denial rates come from CMS Transparency in Coverage PUF PY2026; Medicare Advantage prior-authorization inputs come from CMS OIG / KFF analysis cycles that can lag those two. When an insurer lacks a component, that weight is dropped and the remaining weights are renormalized, missing values are never invented. The letter grade is therefore a peer-relative composite across independently dated sources, not a same-year official rating.

The A-F reputation grade is PlainInsurer's own transparent derived index, computed from the weighted NAIC and CMS components described above - it is not an official rating from NAIC, CMS, or any state insurance regulator, none of which issue a combined letter grade for insurers.

Processing Pipeline

1. NAIC MCAS complaint data is downloaded from the NAIC's public data portal, including complaint ratios, total complaint counts, justified complaints, and market share data for each insurer by state and line of business.
2. CMS Transparency in Coverage PUF data is downloaded from data.healthcare.gov, extracting claim denial rates, prior authorization rates, and appeals outcomes for each health insurance issuer.
3. CMS Medicare Advantage prior authorization data is extracted from OIG reports and KFF analysis publications.
4. Insurers are matched across all three datasets using company names, NAIC codes, and CMS issuer identifiers. Parent-subsidiary relationships are resolved to present consolidated company profiles.
5. Composite scores are calculated for each insurer based on available data, weighted by the components described in the grade calculation methodology above.
6. Letter grades (A through F) are assigned using a bell-curve distribution relative to the full insurer population.
7. All data is loaded into a structured SQLite database serving insurer profiles, state pages, and comparison tools.

Data Vintage and Update Frequency

NAIC MCAS data is released annually, typically in the third quarter, covering complaints from the prior calendar year. CMS Transparency in Coverage PUF data is updated annually under ACA reporting requirements. Medicare Advantage prior authorization data is published as CMS and OIG complete their analysis cycles. PlainInsurer refreshes its database when new data releases become available from any of these sources, typically resulting in one major annual update cycle.

Accuracy Commitment

PlainInsurer reproduces NAIC and CMS data exactly as published. Complaint ratios, denial rates, and appeals outcomes are presented without editorial modification. The grading algorithm is applied consistently using transparent, documented formulas, no subjective adjustments are made for any individual insurer. When data is unavailable for a particular insurer or metric, the grade calculation uses only available components rather than estimating missing values.

Limitations

• Complaint ratios measure formal complaints filed with state insurance regulators, they do not capture unreported customer dissatisfaction, informal disputes resolved directly with the insurer, or social media complaints.
• A high complaint ratio may reflect large market share, complex product lines, or unusual claim types rather than inherently poor service quality. Insurers writing primarily high-value or complex policies may generate more complaints per policy.
• Grades reflect past reporting-period data and do not predict future insurer behavior, financial stability, or claims handling performance.
• Not all insurers have data from all three sources. Health-specific metrics (claim denial rates, prior authorization) are only available for health insurance issuers. Property and casualty insurers are graded primarily on NAIC complaint data.
• This data does not constitute insurance, financial, or legal advice. Always verify current insurer standing with your state department of insurance or a licensed agent. PlainInsurer is not affiliated with NAIC, CMS, or any government agency.

Data Licensing and Reuse

PlainInsurer's own compiled grades, complaint-ratio rankings, and structured-data markup are original PlainInsurer work built on public NAIC and CMS source data. Our documented open-data extract publishes the state-level marketplace claim-denial comparison as CSV and JSON under CC0 1.0; its page explains the scope and denominator. We do not represent that focused extract as a bulk copy of every upstream source dataset.

PlainInsurer runs on AdSense today and accepts no compensation from any insurer, broker, or agent it covers. Any future affiliate placement on a high-intent comparison result would need to meet the same trust bar as the editorial content: clearly labeled as sponsored, deep-linked from an unpaid data-driven ranking that never changes to favor an advertiser, and disclosed prominently next to the link.

Contact

Questions about our methodology? Contact us.