---
title: "Derived US equity risk premium (Sugra-computed)"
method: GET
path: "/api/v1/markets/equity-risk-premium"
tags: ["Economics"]
---

# Derived US equity risk premium (Sugra-computed)

`GET /api/v1/markets/equity-risk-premium`

US equity risk premium computed by Sugra from its own S&P 500 valuation data and US Treasury yields, via a transparent trio of methods (fed_model, cape [headline], gordon). Not a resold vendor table. Every input and its date is disclosed per method. cache 6h.

## Response `200`

Successful Response

- EnvelopeEquityRiskPremiumData
  - `data` EquityRiskPremiumData, required
    - `index` string, required — Equity index (SP500)
    - `headline` string, required — Which method is the headline (cape)
    - `as_of` string, nullable — Headline method's input date (ISO)
    - `risk_free` ErpRiskFree, required
      - `nominal_10y` ErpRate, required
        - `value` number, nullable — Yield in percentage points
        - `date` string, nullable — Observation date (ISO)
        - `source` string, required — Origin series, e.g. FRED:DGS10
      - `real_10y` ErpRate, required
        - `value` number, nullable — Yield in percentage points
        - `date` string, nullable — Observation date (ISO)
        - `source` string, required — Origin series, e.g. FRED:DGS10
    - `methods` ErpMethod[], required — Transparent trio of ERP estimates
      - `method` string, required — fed_model | cape | gordon
      - `kind` string, required — nominal or real premium
      - `equity_risk_premium` number, nullable — ERP in percentage points; null when an input is unavailable
      - `as_of` string, nullable — Oldest input date for this method (ISO)
      - `components` object, required — The exact inputs that produced the premium (auditable)
      - `formula` string, required — Human-readable formula
      - `caveats` string[], required — Method-specific limitations
    - `attribution` string, required — Source attribution (Sugra-computed)
    - `methodology_notes` string[], required — How each premium is derived
  - `meta` SugraMeta, required — Metadata attached to every /api/v1/* response envelope.
    - `endpoint` string, required — Requested endpoint path.
    - `data_time` string, required — ISO 8601 UTC timestamp of the source data, not of the request.
    - `response_time` string, required — ISO 8601 UTC timestamp when this response was produced.
    - `provider` string, required — API name and version.
    - `source` string, nullable — Identifier of the primary upstream source used for this response.
    - `attribution` string, nullable — Human-readable attribution mandated by an upstream source (e.g. a securities regulator or self-regulatory organization). Present only on responses whose source requires the owner and source to be clearly identified. Do not remove or alter it when using the response.
    - `fallback_used` boolean, nullable — True when the primary source failed and a fallback produced the data.
    - `fallback_chain` string[], nullable — Ordered list of sources attempted, in the order they were tried.
    - `cached` boolean, nullable — True when this response was served from the internal cache.
    - `stale` boolean, nullable — True when the cached response was returned after the upstream rate-limited or errored. Clients can use this to detect degraded data.

## Other responses

- `401` — Missing or invalid `x-api-key` header.
- `429` — Daily rate limit exceeded. Check `X-RateLimit-Reset` for the next window.
- `503` — Upstream source is temporarily unavailable. Retry after a short delay.

---

[API](https://skmtc.net/sugra/apis/sugra-api.md) · [All operations](https://skmtc.net/sugra/apis/sugra-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/sugra/sugra-api/versions/dcf7427e6897/schema)