the usd poverty line corresponds to the mean of national poverty lines for the poorest countries of the world while the usd line is the median poverty line found among developing countries as a whole people living with less than usd a day are said to be in extreme poverty the poverty data here concern lowand middleincome countries as categorized in line with world bank definitions aboutcountryclassifications at these low income thresholds poverty rates in highincome countries are close to zero