Where a page shows historical returns, yields, or inflation, the underlying numbers come from public data published by U.S. government agencies and established research libraries. We generally derive our figures from these sources — compounding returns, building growth indices, or adjusting for inflation — rather than republishing raw datasets wholesale. Reference to any source below does not imply that the source endorses Passerine Finance.
Economic and market data
FRED — Federal Reserve Bank of St. Louis.
FRED (Federal Reserve Economic Data) is our main pipeline for economic time series. We use it for the 10-Year U.S. Treasury yield and for Consumer Price Index inflation data. FRED aggregates official series from federal statistical agencies in one well-documented place, which is why it is widely trusted by researchers and journalists. Series update on their own schedules — Treasury yields daily, CPI monthly — and we refresh our local copies from FRED and derive figures such as inflation-adjusted values from them.
Kenneth R. French Data Library — broad U.S. stock market.
Our standard historical stock-market series is built from the Fama/French research factors published by the Kenneth R. French Data Library at Dartmouth's Tuck School of Business. From the monthly market and risk-free returns we compute a total broad-U.S.-market return and compound it into a “growth of $100” index. This is a broad U.S. equity-market return — not the S&P 500 — and it is a long-standing dataset used widely in academic finance. It updates monthly. We explain the choice in more depth in The stock-market data we use.
U.S. Treasury — interest-rate benchmarks.
The 10-Year Treasury constant-maturity yield is the interest-rate benchmark behind several lessons; we retrieve it through FRED. You can explore the stock-and-Treasury history directly in our U.S. Stock Market and 10-Year Treasury data page.
Bureau of Labor Statistics (BLS) — inflation.
The Consumer Price Index we use for inflation adjustments is produced by the Bureau of Labor Statistics and retrieved through FRED. It is the standard measure of consumer price change in the United States and updates monthly.
Rules and reference figures
IRS — contribution limits and tax figures.
Tools that involve retirement accounts or taxes use published reference figures — for example, annual retirement-contribution limits — drawn from IRS publications. These are reference values that change from year to year, not a live data feed, and our tax calculations are deliberately simplified (see our Calculator Methodology).
U.S. Department of Education — federal student loans.
Calculators and articles about federal student loans use the terms set for those programs — rates, limits, and grace periods — as published by the U.S. Department of Education and Federal Student Aid. These figures are set by program rules and updated when the programs change.
Federal Reserve — monetary-policy context.
Where a lesson touches on interest-rate conditions, the context reflects Federal Reserve policy and the rate series it publishes, which we access through FRED.
Several of these Federal Reserve series appear across the site: the effective federal funds rate (FEDFUNDS), the 2-, 10-, and 30-Year Treasury constant-maturity yields (DGS2, DGS10, DGS30), the bank prime loan rate (DPRIME), and the finance rate on 60-month new-auto loans at commercial banks (RIFLPBCIANM60NM). All are produced by the Board of Governors of the Federal Reserve System, distributed through FRED, and in the public domain. Each is shown as a monthly figure in percent (daily series are averaged over the month; months with no observation are left as gaps).
Freddie Mac — mortgage rates.
Our Rates Move Together also charts the 30-Year Fixed Rate Mortgage Average from Freddie Mac's Primary Mortgage Market Survey (FRED series MORTGAGE30US), so mortgage costs can be compared with policy and Treasury rates. Unlike the government series above, this one is copyrighted by Freddie Mac and reprinted with permission — it is not public domain — so we show it with that attribution and keep it in a separate data file.
A note on the data
Public sources, our own calculations.
These sources are public and reputable, but the calculations, charts, and conclusions on Passerine Finance are our own. We do not claim to have created the underlying datasets, we do not imply any agency's endorsement, and we do not attach a license to data we did not produce. If you believe a figure is out of date or incorrect, please tell us through our Contact page.
Related reading: Calculator Methodology · Calculator Testing · Editorial Policy.