Estimating international poverty lines from comparable national thresholds

The World Bank's international poverty line (IPL) of $1.90/day at 2011 PPPs is based on a collection of national poverty lines provided in Ravallion et al. (World Bank Econ. Rev. 23(2), 163-184, 2009), originally used to set the IPL of $1.25/day at 2005 PPPs. This paper proposes an approach for estimating a more recent, complete and comparable collection of national poverty thresholds from reported national poverty rates, and then presents a set of IPLs based on this new database of national poverty lines. In contrast to the lines used to estimate the $1.90 IPL, this approach produces national poverty lines that are (1) consistent with national poverty rates, (2) expressed in common units, and (3) provide greater support to the estimated IPL. These national poverty lines are used to estimate an extreme IPL, and three higher IPLs that are more relevant to higher-income countries. We provide evidence of the robustness and relevance of the $1.90 IPL as a measure of extreme poverty for low-income countries.