in this regard as mentioned above the initial aday poverty line was based on the common national poverty lines of of the poorest countries out of a sample of developing countries studied by ravallion datt and van de walle who used penn ppp values however chen and ravallion after having recomputed this line using penn ppp values and taking the median of the lowest national poverty lines of the same country sample suggested a poverty line of per day they later switched to a new set of ppps for computed by the world bank and suggested a poverty line of per day based on the mean of the poverty lines of the poorest countries of the sample chen and ravallion