About EigenDex
EigenDex is an independent platform for ETF analysis. We build tools that help investors understand what they actually own — and how their portfolio behaves in the real world.
Our Mission
The ETF industry has democratized investing — but it's also created a new problem. With thousands of funds available, it's easy to build a portfolio that looks diversified but is actually 80% the same companies across multiple funds. Hidden overlap, correlated exposures, and compounding expense ratios quietly erode returns without most investors realizing it.
We built EigenDex to make that hidden structure visible. Our tools analyze reported fund holdings from public issuer and market-data sources, historical adjusted prices, and transparent calculations — and present the results in a way that's immediately useful without requiring a finance degree.
Most tools on EigenDex are free and require no account. The core research tools are available without an account. Saved portfolios, change monitoring and scheduled alerts are described on the EigenDex Pro roadmap. We do not provide investment advice and are not affiliated with any fund provider, broker, or financial institution.
What We Build
ETF Overlap Analyzer
Compare reported holdings by position weight, with a visible coverage range and confidence level.
Correlation Finder
Inspect return correlations over explicit observation windows and separate behavior from holdings overlap.
Portfolio Backtester
Test an ETF allocation over the common available history with contributions, costs, rebalancing and a benchmark.
Portfolio X-Ray
Aggregate the underlying positions in multiple ETFs and identify the funds contributing to each exposure.
Expense Ratio Calculator
A 0.50% vs 0.03% expense ratio difference can cost $45,000+ over 30 years on a $100,000 portfolio. See the real numbers.
ETF Explorer
Browse the covered universe by issuer, category and reported-holdings coverage without a proprietary ranking.
Our Data
Holdings data comes from public issuer files and market-data APIs. Coverage varies by fund, so each comparison reports how much of each portfolio is represented. Partial holdings are never rescaled to look complete.
Price data uses adjusted daily closes over the history available in the current dataset. Every analysis displays its latest observation date.
All data carries inherent limitations: holdings reflect point-in-time SEC filings (typically 30–60 day lag), and historical prices may contain gaps or adjustments. Always verify important data with official fund provider sources.
Methodology
Overlap Calculation
Portfolio overlap between two ETFs is calculated using the weighted overlap formula: for each shared holding, we take the minimum weight from each fund, sum these minimums, and express the result as a percentage of the full fund. When either dataset is partial, EigenDex reports the known overlap as a lower bound, a possible upper bound and the coverage of both funds.
Correlation Analysis
Pearson correlation coefficients are computed on aligned adjusted-close daily returns over explicit rolling windows. Correlations closer to +1.0 indicate ETFs that move together; correlations near 0 suggest independence; negative correlations indicate inverse movement.
Backtesting Engine
The backtester uses aligned adjusted-close observations and supports periodic rebalancing, contributions and an explicit annual cost assumption. Results are limited to the common history of every selected asset. Risk metrics use a documented 4% annual risk-free assumption.
Reproducibility
Reports include the observation dates, holdings coverage, calculation version and user inputs needed to reproduce the result. Historical results are descriptive and are not recommendations.
Contact
We welcome feedback, bug reports, and feature suggestions. EigenDex is an independent project and we read every message.
Email:contact@eigendex.com
Website:eigendex.com