Stock Index Seasonality API
The calendar patterns equity traders position around — "Sell in May", the Santa Claus rally, the September swoon — computed live from ~10 years of Yahoo Finance monthly data across the world's major stock indices (no key, nothing stored). Equities have well-documented seasonal tendencies, and this measures them directly: for each index it takes a decade of monthly returns, groups them by calendar month, and returns the average return in each of the twelve months, the share of years that month was positive (the win rate), and the historically strongest and weakest months. The seasonality endpoint returns one index's full 12-month seasonal profile plus the current month's historical bias. The month endpoint flips it around: for a calendar month it ranks every index by its historical average return, so you can see which markets are seasonally strong or weak right now. The indices endpoint lists what is covered, from the S&P 500, Nasdaq, Dow and Russell to the DAX, FTSE, CAC, Euro Stoxx, Nikkei and Hang Seng. The equity-index seasonality / calendar-pattern cut — distinct from the FX, commodity and crypto seasonality APIs, the index price feed and the constituent APIs.
api.oanor.com/indexseasonality-api
