The overall proportion of people living in extreme poverty has fallen, and that trend is projected to continue. It is calculated by converting the national poverty lines from a selection of the poorest countries in the world to a common currency - using purchasing power parity (PPP) exchange rates to adjust for the difference in cost of living across countries - and then taking an average of those lines. It was used to set targets for poverty reduction under the Millennium Development Goals and is now part of the Sustainable Development Goals, which aim to eradicate extreme poverty by 2030. These measures represent levels of poverty above extreme poverty.