Population aging is the central demographic phenomenon of the century, with significant and growing implications to the economy and society. The existing understanding of population aging is based on traditional measures such as old-age dependency ratio and share of elderly population. These are based on a traditional perspective that considers fixed old-age thresholds, such as age 60 or 65. However, age-specific characteristics of population above 60 are different across space and time. Thus, traditional aging measures are not ideal for making cross-country comparisons and do not take into account the multiple dimensions of population aging and do not provide a holistic view of population aging. Several efforts have been made to develop new measures of population aging recently, which accounts for the changing characteristics of the elderly. These measures can be broadly divided into three: (i) adjusted dependency ratios, (ii) multidimensional aging measures, and (iii) measures that use recalculated old-age thresholds. While these measures come up with several unique advantages and benefits, they have their share of drawbacks as well. These measures try to account for the changing characteristics of elderly populations, but they are not simultaneously multidimensional and comparable across different regions. Moreover, most of these recently developed measures of population aging come from developed countries and are thus based on the ideals of well-being among the elderly in the Western world. This chapter provides a critical overview of the existing measures of population aging and throws light on novel measures of population aging that can be comparable across demographically diverse countries.