Data & methodology

This page is the authoritative description of what the calculator does and where the numbers come from.

Sources in this version

World Bank Commodity Price Data (The Pink Sheet)

• Page: https://www.worldbank.org/en/research/commodity-markets
• File: https://thedocs.worldbank.org/en/doc/74e8be41ceb20fa0da750cda2f6b9e4e-0050012026/related/CMO-Historical-Data-Monthly.xlsx
• Terms: https://www.worldbank.org/ext/en/legal/terms-conditions/datasets
• Creative Commons Attribution 4.0 International (CC BY 4.0), subject to the World Bank Dataset Terms
• Source: World Bank Commodity Price Data (The Pink Sheet). Accessed via the World Bank. Licensed under CC BY 4.0 and the World Bank Dataset Terms.
• Fetched: 2026-11-10T06:58:20Z (UTC)

U.S. Bureau of Labor Statistics, Consumer Price Index for All Urban Consumers (CPI-U)

• Page: https://www.bls.gov/cpi/
• File: https://download.bls.gov/pub/time.series/cu/cu.data.1.AllItems
• Terms: https://www.bls.gov/opub/copyright-information.htm
• U.S. government work / public domain. BLS: “You are free to use our public domain material without specific permission, although we do ask that you cite the Bureau of Labor Statistics as the source.” The BLS emblem may not be used.
• Source: U.S. Bureau of Labor Statistics, CPI-U all items, U.S. city average, not seasonally adjusted (CUUR0000SA0). Not an official BLS product; BLS does not endorse this site.
• Fetched: 2026-11-10T06:58:20Z (UTC)

FHFA House Price Index® (Purchase-Only, U.S., not seasonally adjusted, monthly)

• Page: https://www.fhfa.gov/data/hpi
• File: https://www.fhfa.gov/hpi/download/monthly/hpi_master.csv
• Terms: https://www.fhfa.gov/faqs/hpi
• Official FHFA FAQ: the FHFA HPI data are freely available for download. Suggested citation: “Source: FHFA HPI® (Purchase-Only, not seasonally adjusted, nominal).” “FHFA HPI®” and “FHFA House Price Index®” are registered trademarks and must not be used to imply FHFA endorsement.
• Source: FHFA HPI® (Purchase-Only, not seasonally adjusted, nominal), United States monthly index. This site is not endorsed or certified by FHFA.
• Fetched: 2026-11-10T06:58:20Z (UTC)

U.S. Department of the Treasury, Daily Treasury Par Yield Curve Rates (3-month)

• Page: https://home.treasury.gov/resource-center/data-chart-center/interest-rates
• File: https://home.treasury.gov/resource-center/data-chart-center/interest-rates/pages/xml?data=daily_treasury_yield_curve&field_tdr_date_value={year}
• Terms: https://fiscaldata.treasury.gov/api-documentation/
• U.S. government work. Treasury Fiscal Data: “The data is offered free, without restriction, and available to copy, adapt, redistribute, or otherwise use for non-commercial or commercial purposes.” The 3-month wealth index on this site is a derived series computed from those official yields, not a published Treasury total-return index.
• Source: U.S. Department of the Treasury, Daily Treasury Par Yield Curve Rates (3-month). This site is not affiliated with or endorsed by the Treasury.
• Fetched: 2026-11-10T06:58:20Z (UTC)

Inflation adjustment

The CPI-U series (CUUR0000SA0, not seasonally adjusted) is used in two places: the inflation calculator, and the “Adjust for inflation” toggle on asset and compare pages. Toggle results are expressed in start-month dollars: each later nominal value is multiplied by CPI at the start month divided by CPI at that later month. Later monthly contributions are deflated the same way before they are added to “real invested.” Lump-sum real CAGR uses the deflated ending value and the original outlay.

What we compute

Missing months are skipped. The dividend-reinvestment toggle stays disabled because none of the current series is a dividend total-return index.

Sources we considered and did not use

• FRED Coinbase Bitcoin (CBBTCUSD) and Ether (CBETHUSD) — the FRED notes state: “Copyright, 2018, Coinbase. Reproduction of Coinbase data in any form is prohibited except with the prior written permission of Coinbase.” Coinbase’s Market Data terms also forbid displaying or redistributing market data or derived charts to third parties. We did not use these series. CBBTCUSD, Coinbase Market Data Terms.
• FRED as a distributor for other series, including public-domain ones — we download CPI, house prices, and Treasury yields from the originating agencies instead. FRED’s own terms limit the general license to personal, non-commercial use and describe commercial display of even public-domain series more narrowly (internal use, textbooks, newsletters, or reports to clients). The FRED API also forbids storing or redistributing FRED Content. FRED Services Terms of Use.
• CoinGecko (keyless or unpaid) — commercial public display is pointed at paid plans; a full-history keyless request was previously rejected (error 10012).
• CryptoCompare / CCData standard API — license is internal use only and forbids display unless CCData agrees in writing.
• Coin Metrics community archives — CC BY-NC 4.0, which does not fit an ad-supported site.
• Yahoo Finance, Stooq, and Coinbase Market Data directly — automated collection, redistribution, or public display is forbidden or limited to personal use.
• Wikipedia / Wikimedia price charts — no complete monthly BTC or ETH price table suitable for this calculator was found under a clear data license we could rely on.
• Kaggle and similar “CC0” crypto CSVs — these are typically re-uploads of exchange or aggregator data; a later CC0 tag does not replace the original provider’s terms.
• S&P 500 and Case-Shiller house prices via FRED — third-party copyright; written permission required.
• FDIC national deposit rates — useful in principle, but the open-data page we read did not include a reuse statement as clear as BLS, FHFA, or Treasury Fiscal Data, so they were left out.

Individual stocks and equity ETFs (AAPL, MSFT, SPY, QQQ, and similar) and Bitcoin and Ether are therefore not included. They can be added later if a clearly licensed (or paid) source is obtained, without redistributing a prohibited feed.

Unit tests for the math live in tests/calc.test.js and are run with Node’s built-in test runner. Data files are refreshed with python3 tools/refresh-data.py.

Data: World Bank Commodity Price Data (CC BY 4.0), FHFA HPI®, U.S. Treasury yields, BLS CPI-U. Historical illustration, not financial advice; ignores fees, storage and taxes. Details