Unit for economic variables: Billion US dollars to Million Euros

[hettieboonman]

Hi all,

During the teams meeting this morning the following issue was discussed.
Currently, some of the economic variables have unit 'billion US dollars', others 'million euros'. Some variables like GDP should also be available in million euros.

It seemed like 'million euro's is more suitable unit for economic variables, because this is the unit that is used within the models (of people that were present this morning).
The question that was raised was: 'Why was initially the choice for billion US dollars made'?

Two possibilities were discussed:

Possibility 1:

• Variables like GDP can have 2 possible units. The database will indicate which unit is used for this economic variable.

Possibility 2:

• We have to make a decision between million euro's and billion dollars. It seems like the preference lies with 'million euros'.

@erikfilias and @danielhuppmann could you take a look at this issue? (Erik was present this morning).

Greets, Hettie

[erikfilias]

Thanks, @hettieboonman, for this issue. It helps us to clarify and find an agreement. From my perspective, modeling teams have to use aggregation or conversion tools to interact with the common nomenclature. Thus, I agree with Possibility 2 to use Billion US dollars, and modeling teams should use conversion tools; even the pyam package provides us with some functions. Please check section 2.2 of the guideline at the end of the doc. Also, more details can be found here.
@openENTRANCE/coordination , @openENTRANCE/modellers , any suggestion?

[tburandt]

As openEntrace is an EU/Europe-focussed project and as far as I know many models in the consortium use Euros/mln Euros already as inputs or outputs for their models, I think it would be better to use million euro as a common unit. In general, I would also prefer @hettieboonman 's second possibility, of just having one unit, instead of two.

[hettieboonman]

Hi all, thank you for picking this up Erik. My preference would also be million euro, when we pick one of the two units.

greets, Hettie

[paopis]

Hi all, Million Euro is the preferred unit also for me.
It is what we also use in our model.
Most of the literature I have found also is in Million Euros.

[danielhuppmann]

Thanks @hettieboonman et al for the discussion so far. I think we should actually implement both options:

1. go through all definitions so far and harmonize to Euro (including harmonizing to the order of magnitude and nominal/real where possible)

2. allow lists of possible units. This can be easily implemented in a yaml-notation as either

       unit:
         - '%'
         - billion US$2010/yr
         - ''
   

   or

       unit: ['%', billion US$2010/yr, '']
   

[hettieboonman]

Dear Daniel,

In that case I agree, at least everywhere where "billion US$2010/yr" was the unit, the following unit could be added: "million euro/yr" in the list with unit-options.

Greets, Hettie

[danielhuppmann]

See this related issue by @sandrinecharousset #85.