The outside world

Every series here has a stated mechanism.

Nothing is a ticker widget. A series earns a place only if there is a path by which it changes what you can afford — and that path is written down, so you can disagree with the mechanism rather than distrust a number.

6 of 18 series ready6 providers need no key9 awaiting a free key

Live now

Treasury average interest rate

U.S. Department of the Treasury

3.71%

+12.2% y/y

What risk-free money earns. Sets the floor for whether your savings are keeping up or quietly losing ground.

0.0%3.0%6.0%Jan 31Apr 30Jun 30

Heating degree days

NOAA / National Weather Service

How cold it actually was, in the units utilities bill by. This is the causal input the seasonal model currently only approximates.

No data returned

National Weather Service returned no usable observations

NOAA / National Weather Service

S&P 500

Stooq

Relevant to a household only through what it does to a position you actually hold. Here it feeds the scenario engine, not a ticker widget.

No data returned

Stooq returned no usable observations

Stooq

Total US market (VTI)

Stooq

A better proxy than the S&P for what most index investors actually own.

No data returned

Stooq returned no usable observations

Stooq

USD to EUR

European Central Bank via Frankfurter

0.88

+3.3% y/y

For anyone earning in one currency and spending in another, this is a contractual line item, not a curiosity.

0.860.88Mar 18May 25Jul 24

Bitcoin

CoinGecko

65,362.06

−44.6% y/y

Included because people hold it. Its volatility is exactly why coupling a position to a cash-flow forecast beats staring at the price.

60,00070,00080,000Apr 29Jun 13Jul 26

Inflation

Scales the discretionary block. Your historical spending days are denominated in old dollars.

  • CPI, all itemsNeeds FRED_API_KEYmonthly

    The general price level. Rises here scale the whole discretionary block, because last year's grocery days no longer cost what they cost.

    U.S. Bureau of Labor Statistics via FRED

  • CPI, groceriesNeeds FRED_API_KEYmonthly

    Food at home, specifically. Usually the largest discretionary line in a household ledger, and it moves differently from headline CPI.

    U.S. Bureau of Labor Statistics via FRED

  • CPI, rent of primary residenceNeeds FRED_API_KEYmonthly

    Where your largest contractual line is heading at renewal. Rent does not drift month to month — it steps, and this predicts the step.

    U.S. Bureau of Labor Statistics via FRED

Interest rates

Reprices variable debt and sets what savings earn.

  • Federal funds rateNeeds FRED_API_KEYmonthly

    The anchor for everything variable you owe. Card APRs and adjustable loans follow this with a short lag.

    Federal Reserve via FRED

  • 30-year fixed mortgage averageNeeds FRED_API_KEYweekly

    Determines what a house costs per month, which is the single largest conditional most households ever run.

    Freddie Mac via FRED

  • Treasury average interest ratereadymonthly

    What risk-free money earns. Sets the floor for whether your savings are keeping up or quietly losing ground.

    U.S. Department of the Treasury

Energy prices

Feeds the quasi-fixed categories almost one-for-one.

  • Retail gasoline, all gradesNeeds EIA_API_KEYweekly

    Multiplies straight through the fuel category. One of the few macro series with a same-month effect on a household ledger.

    U.S. Energy Information Administration

  • Residential electricity priceNeeds EIA_API_KEYmonthly

    The per-kWh rate behind your utility bill. Combined with degree days, this is the whole bill.

    U.S. Energy Information Administration

  • Residential natural gas priceNeeds EIA_API_KEYmonthly

    Heating cost per unit. In a northern climate this is the difference between a $90 January and a $220 one.

    U.S. Energy Information Administration

Weather

The physical driver behind heating and cooling bills, in the units utilities bill by.

  • Heating degree daysreadydaily

    How cold it actually was, in the units utilities bill by. This is the causal input the seasonal model currently only approximates.

    NOAA / National Weather Service

Jobs & wages

Conditions the income distribution and the slack you should leave in it.

  • Unemployment rateNeeds FRED_API_KEYmonthly

    Context for how much slack to leave in the income assumption. A forecast that models salary as near-certain is wrong in the wrong direction.

    U.S. Bureau of Labor Statistics via FRED

  • Real average hourly earningsNeeds FRED_API_KEYmonthly

    Whether wages are actually outpacing prices. The honest answer to 'am I falling behind' rather than the vibes answer.

    U.S. Bureau of Labor Statistics via FRED

  • Personal saving rateNeeds FRED_API_KEYmonthly

    What everyone else is managing to keep. Useful as a reference point, dangerous as a target — your obligations are not theirs.

    U.S. Bureau of Economic Analysis via FRED

Housing

Moves the largest line on most balance sheets, owned or rented.

  • Case-Shiller national home price indexNeeds FRED_API_KEYmonthly

    Moves the asset side if you own, and the rent side eventually if you do not.

    S&P Dow Jones Indices via FRED

Equities

Only reaches your cash flow through a position you hold. Coupled, not displayed.

  • S&P 500readydaily

    Relevant to a household only through what it does to a position you actually hold. Here it feeds the scenario engine, not a ticker widget.

    Stooq

  • Total US market (VTI)readydaily

    A better proxy than the S&P for what most index investors actually own.

    Stooq

Currency

A real recurring cost when income and spending sit in different currencies.

  • USD to EURreadydaily

    For anyone earning in one currency and spending in another, this is a contractual line item, not a curiosity.

    European Central Bank via Frankfurter

Crypto

Held by enough people that ignoring it would be a modeling choice, not neutrality.

  • Bitcoinreadydaily

    Included because people hold it. Its volatility is exactly why coupling a position to a cash-flow forecast beats staring at the price.

    CoinGecko

Providers

U.S. Treasury Fiscal Data

no key needed

Daily Treasury yield curve and par rates, straight from the source.

Terms
Public domain. No key, no quota.
Docs
fiscaldata.treasury.gov/api-documentation/

Frankfurter (ECB)

no key needed

Daily foreign exchange reference rates published by the European Central Bank.

Terms
Free, no key, no quota.
Docs
frankfurter.dev

World Bank Open Data

no key needed

Annual macroeconomic indicators for nearly every country.

Terms
CC BY 4.0. No key.
Docs
datahelpdesk.worldbank.org/knowledgebase/topics/125589

Stooq

no key needed

End-of-day prices for indices, equities, and commodities as plain CSV.

Terms
Free for personal use. No key. Be polite with request volume.
Docs
stooq.com/db/h/

National Weather Service

no key needed

Observations and forecasts, including the degree days that drive heating bills.

Terms
Public domain. No key. Send a descriptive User-Agent.
Docs
www.weather.gov/documentation/services-web-api

CoinGecko

no key needed

Cryptocurrency prices and history.

Terms
Public tier works without a key at low volume; a free key raises limits.
Env
COINGECKO_API_KEY
Docs
docs.coingecko.com/reference/introduction

FRED (St. Louis Fed)

free key

Hundreds of thousands of US economic series — inflation, rates, employment, housing.

Terms
Free key, issued immediately. Generous quota.
Env
FRED_API_KEY
Docs
fred.stlouisfed.org/docs/api/api_key.html

U.S. Energy Information Administration

free key

Retail electricity, natural gas, and gasoline prices by state.

Terms
Free key, issued immediately.
Env
EIA_API_KEY
Docs
www.eia.gov/opendata/

Bureau of Labor Statistics

free key

CPI, employment, and wage series direct from BLS.

Terms
Free key. 500 queries/day registered, 25 unregistered.
Env
BLS_API_KEY
Docs
www.bls.gov/developers/

Alpha Vantage

free key

Equities, FX, and commodities with a generous free key but a tight daily cap.

Terms
Free key. Roughly 25 requests/day — cache aggressively.
Env
ALPHAVANTAGE_API_KEY
Docs
www.alphavantage.co/documentation/

Finnhub

free key

Equity quotes, fundamentals, and candles on a workable free tier.

Terms
Free key. 60 calls/minute.
Env
FINNHUB_API_KEY
Docs
finnhub.io/docs/api

Tiingo

free key

Clean end-of-day equity history, well maintained.

Terms
Free key. 500 requests/day, 50 unique symbols/month.
Env
TIINGO_API_KEY
Docs
www.tiingo.com/documentation/general/overview

Polygon.io

free key

Aggregated market data with a free delayed tier.

Terms
Free key. 5 calls/minute, end-of-day only.
Env
POLYGON_API_KEY
Docs
polygon.io/docs

Twelve Data

free key

Equities, ETFs, FX, and crypto through one consistent interface.

Terms
Free key. 800 requests/day, 8/minute.
Env
TWELVEDATA_API_KEY
Docs
twelvedata.com/docs

Financial Modeling Prep

free key

Prices plus company fundamentals on a free tier.

Terms
Free key. 250 requests/day.
Env
FMP_API_KEY
Docs
site.financialmodelingprep.com/developer/docs

Open collections

Imagery in this product is generated from data rather than sourced, for reasons argued on the design page. These open collections are here for the handful of editorial surfaces where a real artifact earns its keep — all CC0 or public domain, all with working APIs.

  • Smithsonian Open AccessNational Numismatic Collection — currency, bonds, stock certificatesFree key via api.data.gov. 4.5M+ CC0 items.free keyCC0
  • RijksmuseumDutch Golden Age — including VOC share certificates, the first traded stockFree key. The most historically apt collection for this product.free keyPublic domain
  • The Metropolitan Museum of ArtPrints, engravings, commerce and trade imageryNo key at all. 490k+ objects, ~half CC0.no keyCC0
  • Cleveland Museum of ArtOpen access collection, strong graphic and print holdingsNo key. Clean JSON, generous CORS.no keyCC0
  • Library of CongressWPA posters, financial ephemera, Depression-era photographyNo key. Append ?fo=json to nearly any collection URL.no keyPublic domain (varies)