---
title: "Single-variable Penn World Table time series for one country"
method: GET
path: "/api/v1/research/pwt/country/{iso3}/{variable}"
tags: ["Research"]
---

# Single-variable Penn World Table time series for one country

`GET /api/v1/research/pwt/country/{iso3}/{variable}`

Returns a lean `(year, value)` series for one Penn World Table variable for one ISO 3166-1 alpha-3 coded country. Useful for charting a single metric over time without pulling the full 47-column panel. The variable name must match a Penn World Table column exactly. Popular picks: `rgdpo` (output-side real GDP), `rgdpe` (expenditure side), `cn` (capital stock), `hc` (human capital index), `ctfp` (TFP level), `labsh` (labor share of income). Call `/api/v1/research/pwt/definitions` for the complete variable dictionary. Published under CC BY 4.0 with attribution to Penn World Table (Feenstra, Inklaar & Timmer, University of Groningen).

## Path parameters

- `iso3` string, required — ISO 3166-1 alpha-3 country code. Case-insensitive; normalised to uppercase.
- `variable` string, required — Penn World Table variable name (e.g. `rgdpo`, `cn`, `hc`, `ctfp`, `labsh`).

## Query parameters

- `start_year` integer, nullable — Inclusive start year (integer). Panel range starts 1950.
- `end_year` integer, nullable — Inclusive end year (integer). Defaults to the latest year in the panel.
- `version` string, nullable — Release selector. `pwt1100` (default) or `pwt1001` (legacy).

## Response `200`

Year-value pairs for one variable plus variable description and type.

- EnvelopePwtCountryVariablePayload
  - `data` PwtCountryVariablePayload, required — Single-variable time series for one country.
    - `version` string, required — Release identifier.
    - `countrycode` string, required — ISO 3166-1 alpha-3 code echoed from the path, uppercased.
    - `country` string, nullable — Country name.
    - `variable` string, required — Variable name requested from the path.
    - `description` string, nullable — Variable definition from the release Legend sheet.
    - `type` string, nullable — Variable group (e.g. `real-gdp-ppp`, `national-accounts`, `data-flag`).
    - `observations` PwtMetricObservation[], required — Year-value pairs ordered ascending by year.
      - `year` integer, required — Observation year.
      - `value` number, nullable — Variable value, or null when not published for that country-year.
    - `count` integer, required — Number of observations in the response.
    - `start_year` integer, nullable — Inclusive start year applied, or null.
    - `end_year` integer, nullable — Inclusive end year applied, or null.
    - `attribution` string, required — CC BY 4.0 attribution.
  - `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.
- `422` — Validation Error
- `429` — Daily rate limit exceeded. Check `X-RateLimit-Reset` for the next window.
- `503` — Upstream source is temporarily unavailable. Retry after a short delay.

---

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