SPDR S&P 500 ETF Trust - proxy for S&P 500 index (15-min delayed)
Why: S&P 500 proxy. Bitcoin correlation with SPY determines whether macro equity moves drag or lift crypto.
Category: macro. Macro economic indicators track monetary policy, liquidity conditions, and traditional market positioning. Changes in these metrics often lead Bitcoin price moves by days or weeks.
Source: Finnhub. Updated: 15-min delayed (market hours).
API: GET /api/metrics/etf-spy