The unidad de inversión (UDI, literally "investment unit", ISO 4217 code MXV) is an index unit of funds used in Mexico.
Unlike currencies, it is designed to maintain a constant purchasing power with respect to the general consumer price index and not be subject to inflation.
The Mexican credit system (especially mortgages) uses the UDI rather than the peso because of its stability.
[1] The plural form "UDIs" is often used, even in official government documents, but is regarded as grammatically incorrect.
The following is a table of the value of the unidad de inversión on selected dates: