Change GDP deflator for EUR and add factor for EUR_2024

[mwerning]

This PR:

• Adds EUR_2024 as a currency. cf. iiasa/sparccle-workflow#19
• Changes the deflators used for EUR to be Eurozone-wide values, rather than specific Germany. See discussion below.

[danielhuppmann]

Thanks, but I'm confused why GDP deflator provided by the World Bank is not correct and has to be modified in this way. Why does the USD deflator not have to be modified in this manner?

Please also add the script that you used to query the data from the World Bank, modify the values, and write the relevant lines. This will help to add more values easily (e.g., 2025 EUR.

[mwerning]

@danielhuppmann The World Bank provides different indicators. There is the NY.GDP.DEFL.ZS.AD indicator, which provides the GDP deflator as a linked series. This is only available on the country level though. For the Euro area, the World Bank does provide data, but the indicator is NY.GDP.DEFL.KD.ZG, which is an annual %, therefore the calculation is needed. I mentioned this to @khaeru, as having an indicator that is available for the entire Euro area seemed more accurate than just using the deflator for Germany, and we discussed to update the definitions accordingly.

Due to time constraints, I didn't download the data using a script, but manually by using the Download option on the World Bank website and did the calculation in Excel. Happy to attach the spreadsheet here if that helps.

GDP_deflator_calc_EUR.xlsx
API_NY.GDP.DEFL.KD.ZG_DS2_en_csv_v2_104.csv

[khaeru]

EDIT: Ah, I was too slow.

To frame another way:

• NY.GDP.DEFL.ZS (previous)
  • Used for USD and formerly EUR.
  • This data flow does not have generic/EUR-wide values.
  • The EUR deflators were for Germany specifically (?locations=DE in the URL in the file), which could be a worse fit for data (a) about the EU as a whole (e.g. its total GDP) or (b) for other countries in the Eurozone where inflation went at different rates.
• NY.GDP.DEFL.KD.ZG
  • This does include EUR-wide values (?locations=XC).

This to me seemed like sound logic, so I encouraged to open the PR.

There many more nuances we could get into. For example, if USD_#### is used to express quantities describing a specific non-USA country (say: Ghana), then in some sense that country's own domestic deflators should be used to change to a different base year, and not the ones of the country (USA) whose currency happens to be picked as units of measurement. But to support choice or detection of this would be a big expansion of scope for the package.

[khaeru]

@mwerning the test workflow had been disabled by GitHub for inactivity. I've reenabled it. If you push a new commit or force-push a small change to the existing one, it should run again.

[khaeru]

a new commit

You should for instance add yourself to AUTHORS.

[mwerning]

@khaeru Thank you for the more detailed explanation. I have added today's date to the definitions.txt as the date for the last update for the EUR values and modified the AUTHORS.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.01%. Comparing base (87b823b) to head (44b756b).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

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[khaeru]

Thanks @mwerning for this helpful contribution! 🥳