PPP can be used to convert national accounts data, like GDP and its expenditure components, into a common currency, while also eliminating the effect of price level differences between countries. They can also be used to derive price level indexes (PLIs), the ratio of a country’s PPP to its market exchange rate, to directly compare price levels across countries.

PPPs and the PLIs and real (or PPP-adjusted) expenditures to which they give rise allow for many use-cases, but they are particularly valuable for empirical work involving comparisons of per capita consumption or levels of GDP (or other GDP aggregates) across countries and for the measurement of global poverty and global income inequality. The breadth and depth of ICP data allows its use-cases to cover other areas of economics, including empirical analyses of economic growth, productivity and trade, and even beyond, for instance, to help track global targets such as the UN Sustainable Development Goals related to health, education, energy and emissions and labor. Other applications of ICP data include their use in the construction of indexes, for example cost-of-living measures. Uses-cases can even be extended into the policymaking domain at all levels (global, regional and national) given the increased importance of cross-country benchmarking, among other possibilities.

Recommended uses of PPPs include: To make spatial comparisons of GDP and its expenditure components | To make spatial comparisons of price levels | To group countries by their per capita volume indexes and price level indexes

Recommended uses of PPPs with limitations  include: To analyze changes over time in relative GDP per capita and relative prices | To analyze price convergence | To make spatial comparisons of the cost of living | To use PPPs calculated for GDP and its expenditure components as deflators for other values.
PPP conversion factor, private consumption (LCU per international $)
Global PPP estimates provided by ICP are produced by the ICP Global Office and regional implementing agencies, based on data supplied by participating countries, and in accordance with the methodology recommended by the ICP Technical Advisory Group and approved by the ICP Governing Board. As such, these results are not produced by participating countries as part of their national official statistics.

PPPs are not recommended use: As a precise measure to establish strict rankings of countries | As a means of constructing national growth rates | As a measure to generate output and productivity comparisons by industry | As an indicator of the undervaluation or overvaluation of currencies | As an equilibrium exchange rate.
Purchasing power parity (PPP) conversion factor is a spatial price deflator and currency converter that controls for price level differences between countries, thereby allowing volume comparisons of gross domestic product (GDP) and its expenditure components. This conversion factor is for household final consumption expenditure.
PPPs are both currency conversion factors and spatial price indexes. PPPs convert different currencies to a common currency and, in the process of conversion, equalize their purchasing power by controlling differences in price levels between countries.

Typically, higher income countries have higher price levels, while lower income countries have lower price levels (Balassa-Samuelson effect). Market exchange rate-based cross-country comparisons of GDP at its expenditure components reflect both differences in economic outputs (volumes) and prices. Given the differences in price levels, the size of higher income countries is inflated, while the size of lower income countries is depressed in the comparison. PPP-based cross-country comparisons of GDP at its expenditure components only reflect differences in economic outputs (volume), as PPPs control for price level differences between the countries. Hence, the comparison reflects the real size of the countries.

The International Comparison Program (ICP) estimates PPPs for the world’s countries. The ICP is conducted as a global partnership of countries, multilateral agencies, and academia. The most recent 2017 ICP comparison covered 176 countries, including 47 Eurostat-OECD countries. For countries that have not participated in ICP comparisons, the PPP are imputed based on a regression model.

ICP estimated PPPs cover years from 2011 to 2017. WDI extrapolates 2011 PPPs for years earlier years, and 2017 PPPs for later years. Description of WDI extrapolation approach is available here: https://datahelpdesk.worldbank.org/knowledgebase/articles/665452-how-do-you-extrapolate-the-ppp-conversion-factors

For the member countries of Eurostat-OECD PPP Programme, PPP conversion factors are periodically updated based on the organizations’ databases. For Eurostat-OECD PPP Programme, please refer to the following websites.
(http://www.oecd.org/sdd/prices-ppp/)
(https://ec.europa.eu/eurostat/web/purchasing-power-parities/overview)

For more information on the ICP and PPPs, please refer to the ICP website at https://www.worldbank.org/en/programs/icp.