New SSC package: wdi_deflate: Convert monetary values across PPP, USD, and LCU

[Kalle Hirvonen]

Introducing wdi_deflate, a Stata package for converting monetary variables — such as consumption, income, or expenditure from household surveys — to purchasing power parity (PPP) international dollars, nominal US dollars, or constant local currency units (LCUs) using World Bank World Development Indicator (WDI) data.

Thanks to Kit Baum, wdi_deflate is available from SSC for Stata version 15 and higher. To install, type: ssc install wdi_deflate.

The module downloads PPP conversion factors, Consumer Price Index (CPI), and official exchange rates from the WDI and applies them in a single command. Seven conversion paths are supported, including LCU→PPP, LCU→USD, CPI deflation, and rebasing across ICP rounds. It handles both cross-sectional and panel data.

Here's a quick illustration. Suppose you have household consumption and income data in local currency for Ethiopia and Tanzania, collected in different years, and you want to convert to 2021 PPP international dollars:

clear
input str3 iso3 int year double consumption double income
"ETH" 2018 15000 22000
"TZA" 2019 850000 1200000
end
wdi_deflate consumption income, country(iso3) from(year) to(2021)
list

This creates consumption_ppp2021 and income_ppp2021. Private consumption PPP is the default; add usd for nominal US dollars, deflate for constant LCU, or gdp for GDP-based PPP. WDI data are downloaded automatically.

For reproducible research, you can save a deflator snapshot and reference it in subsequent conversions.

clear
wdi_deflate build, saving(deflator.dta) countries(ETH TZA)  
clear
input str3 iso3 int year double consumption
"ETH" 2018 15000
"TZA" 2019 850000
end
wdi_deflate consumption, country(iso3) from(year) to(2021) using(deflator.dta)
list

wdi_deflate requires wbopendata (ssc install wbopendata) and tknz (ssc install tknz).

For more details, type help wdi_deflate after installation. Feedback and suggestions are welcome.