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Garden step

The Garden step is where most of the work falls in. This is where the data manager needs to carefully look at the data, filter outliers, harmonize labels (e.g. country names), improve the dataset metadata, etc.

Garden steps typically depend on meadow steps. For instance, the garden step data://garden/un/2022-07-11/un_wpp, which generates the dataset World Population Prospects (UN, 2022), depends on this same process but in meadow: data://meadow/un/2022-07-11/un_wpp. That is, the meadow step has done some pre-liminary (and minor) work on re-shaping the UN WPP dataset and now is the turn of the garden step to apply the major processing steps to have a curated UN WPP dataset by Our World in Data.

A typical flow up to the Garden step could look like:

flowchart LR

    upstream1((____)):::node -.->|copy| snapshot1((____)):::node
    snapshot1((____)):::node -->|format| meadow1((____)):::node
    meadow1((____)):::node -->|harmonize| garden1((____)):::node

    subgraph id0 [Upstream]

    subgraph id1 [Snapshot]

    subgraph id2 [Meadow]

    subgraph id3 [Garden]

    subgraph id [ETL]

    classDef node fill:#002147,color:#002147
    classDef node_ss fill:#002147,color:#fff

However, garden steps could also depend on other garden steps. This is often the case for datasets containing long-run indicators, where different garden datasets are combined.

Long-run indicators

A long-run indicator is an indicator that has datapoints spanning over a broad period of time and that typically relies on multiple sources.

For instance, we have a population indicator that combines data from the UN and other sources that goes back to 10,000 BCE. In particular, it uses data from the UN, Gapminder and HYDE.

This is how the dependency graph our population indicator looks like:

  - data://garden/hyde/2017/baseline
  - data://garden/gapminder/2023-03-31/population
  - data://garden/un/2022-07-11/un_wpp
  - data://open_numbers/open_numbers/latest/gapminder__systema_globalis

TODO: Add an example of code

Harmonizing labels

In order to understand data within a single dataset, we want to know what is meant by the data.

For example, a country column containing the value Korea could be referring to South Korea, North Korea, or historical unified Korea as it existed a century ago, depending on the context and the intent of the data provider.

Harmonization is the editorial process by which we modify the indexing columns for a dataset to ensure that the data is consistent and unambiguous.

What does Our World in Data harmonize?

Today, Our World in Data makes a best-effort to harmonize countries and regions. We strive to do this in a way that is consistent with the ISO 3166-1 standard, however we use custom editorial labels for countries and regions that are often shorter than those in the standard, in order to make data visualisations richer and more understandable.

Since we also present long-run datasets over multiple centuries, a time period in which national borders have changed, split and merged, we also make a best-effort attempt to harmonize the names of historical countries and regions that no longer exist and are not present in the ISO standard.

How do we perform harmonization?

There are two methods that we use, both of which are semi-automated and involve some human judgement by our data managers.

Command-line harmonization

Recommended method

The etl codebase contains an interactive harmonize command-line tool which can be used to harmonize a CSV file that contains a column with country names.

$ poetry run etl-harmonize --help

 Given a DATA_FILE in feather or CSV format, and the name of the COLUMN representing country
 or region names, interactively generate the JSON mapping OUTPUT_FILE from the given names to
 OWID's canonical names. Optionally, can use INSTITUTION to append "(institution)" to

 When a name is ambiguous, you can use:
 - Choose Option (9) [custom] to enter a custom name
 - Type `Ctrl-C` to exit and save the partially complete mapping
 If a mapping file already exists, it will resume where the mapping file left off.

╭─ Options ───────────────────────────────────────────────────────────────────────────────────╮
│ --help      Show this message and exit.                                                     │

As an example, start the harmonization interactive session for table undp_hdr from dataset meadow/un/2022-11-29/undp_hdr, which has country column with the raw country names:

$ poetry run harmonize data/meadow/un/2022-11-29/undp_hdr/undp_hdr.feather country mapping.json
206 countries/regions to harmonize
   189 automatically matched
   17 ambiguous countries/regions

Beginning interactive harmonization...
  Select [skip] to skip a country/region mapping
  Select [custom] to enter a custom name

? [1/17] Arab States: (Use shortcuts or arrow keys)
 » 1) Yemen Arab Republic
   2) United States Virgin Islands
   3) United States Minor Outlying Islands
   4) United States
   5) United Arab Emirates
   6) [custom]
   7) [skip]

The output mapping is saved in mapping.json.

Using the Grapher admin

This method is not preferred. Instead, consider using the etl-harmonize command tool.

The owid-grapher codebase contains a interactive country harmonization tool that can be accessed at http://localhost:3030/admin/standardize when running the dev server.

To use the tool, you upload a CSV file containing a column called Country, and indicate the encoding of country names.

For staff

The interactive harmonization tool for staff is available at


After adapting and processing the origin's data, we have a curated dataset. This dataset, contains indicators (maybe not present in the origin) that we need to properly document.

The metadata in Garden consists mainly of two objects: dataset and tables. The metadata comes as a YAML file next to the processing scripts.