---
title: "World GDP per capita and population aggregate time series"
method: GET
path: "/api/v1/research/maddison/world"
tags: ["Research"]
---

# World GDP per capita and population aggregate time series

`GET /api/v1/research/maddison/world`

Returns the world aggregate series from the Maddison Project's `Regional data` sheet. Covers world GDP per capita in 2011 international dollars (PPP) and world population in thousands of people. The Maddison world aggregate is population-weighted across the member countries where data are available. Pre-1950 observations land on the Maddison milestone year grid (1820, 1830, 1840, 1870, 1890, 1900, 1913, 1929, 1938); annual from 1950 through 2022. Do not assume uniform spacing before 1950. Published under CC BY 4.0 by Bolt and van Zanden at the University of Groningen.

## Query parameters

- `start_year` integer, nullable — Inclusive start year (integer). World series begins at 1820.
- `end_year` integer, nullable — Inclusive end year (integer). Defaults to 2022.

## Response `200`

Year-ordered world observations with gdppc and pop.

- EnvelopeMaddisonWorldPayload
  - `data` MaddisonWorldPayload, required — World aggregate time series drawn from the `Regional data` sheet.
    - `region` string — Fixed identifier `World` for this endpoint.
    - `observations` MaddisonWorldObservation[], required — Year-ordered world aggregate observations. Pre-1950 points land on the Maddison milestone grid (1820, 1830, 1840, 1870, 1890, 1900, 1913, 1929, 1938); annual from 1950.
      - `year` integer, required — Observation year.
      - `gdppc` number, nullable — World GDP per capita, 2011 international dollars (PPP), population-weighted aggregate.
      - `pop` number, nullable — World population, thousands of people.
    - `count` integer, required — Number of world observations returned.
    - `start_year` integer, nullable — Inclusive start year applied, or null if unbounded.
    - `end_year` integer, nullable — Inclusive end year applied, or null if unbounded.
  - `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. JSON body with a stable `code` distinguishing `missing_api_key` (no header sent) from `invalid_api_key` (header sent, key not accepted); any other 401 source carries the generic `unauthorized` with its detail as `reason`. Plus `hint`. `plan` is always null on 401 - an unauthenticated request has no plan; quota exhaustion is 429, not 401.
- `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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