What other poverty lines do the World Bank use in tracking progress against global poverty?
The World Bank has different poverty lines to measure monetary poverty. First, the international poverty line (IPL) is used to measure extreme poverty. This line is most relevant for measuring poverty in low-income countries. For richer countries, two higher lines are more relevant for measuring poverty. With 2017 PPPs, these lines are $3.65 for lower-middle-income countries and $6.85 for upper-middle-income countries. For more technical details, see Jolliffe and Prdyz (2016) and Jolliffe and al. (2022) for the derivation of the international poverty line and higher lines with the 2011 and 2017 PPPs, respectively.
The World Bank also uses a societal poverty line (SPL) that reflects a more relative concept of poverty. With 2011 PPPs, the SPL is defined as $1.00 plus half the median level of consumption in a country, or the international poverty line if $1.00 plus half the median level of consumption is lower than the international poverty line. This line increases as a country grows (and the median increases). The societal poverty line with the 2017 PPPs is $1.15 plus half the median level of consumption in a country, or the international poverty line if $1.15 plus half the median level of consumption is lower than the international poverty line.