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 4?-place function taking as parameters:

• The source currency
• The target currency
• The location with respect to the PPP calculation?
• The year

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

Of these, the Geary–Khamis dollar partially fixes the parameters except the year. 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.

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.

mysql> 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)