Geary–Khamis dollar

The Geary–Khamis dollar (also known as the international dollar) is a hypothetical currency.

As a function

Currency conversions involving PPP can be conceptualized as a 6-place function taking as parameters:

• Target currency
• Year associated with the currency
• Location with respect to the PPP calculation (this is almost always the location where the target currency is used)
• Year associated with the location (this is almost always the same as the year associated with the currency)
• Some basket of goods
• Price index/aggregation method/PPP formula

Only after fixing all the parameters can the unit make sense next to a number.

Of these, the Geary–Khamis dollar partially fixes the parameters except the two year parameters. Specifically, it sets the target currency to be the US dollar and the location to the United States. Therefore formally the Geary–Khamis dollar can be seen as a "unit schema" or "unit-producing function" that takes a year as input and outputs an actual unit.

On the source side:

• Source currency
• Year associated with the currency

Difference with the US dollar for a particular year

e.g. 2000 GK dollar vs 2000 US dollar

Is there a difference?

Devec database

Multiple metrics in the devec database use the Geary–Khamis dollar (at various years) for units. At the MySQL prompt:

select metric,units from data
where region = 'Japan' and units REGEXP 'international dollar'
group by metric,units;

The where region = 'Japan' is just to restrict the search space, since region is an indexed column in the table.

External links

• Geary–Khamis dollar (Wikipedia)