Accurate, consistent and timely data on global trends in population age structure are critical for assessing current and future needs with respect to population ageing and for setting policy priorities to promote the well-being of the growing number and share of older persons in the population. This publication presents the highlights of the World Population Ageing 2017 report, which summarizes the trends in population ageing drawn from the latest United Nations estimates and projections of population by age and sex, as published in World Population Prospects: The 2017 Revision. The present Highlights includes a special focus on trends in the household living arrangements of older persons - whether alone, with a spouse or with own children - reflecting newly compiled estimates from the United Nations Database on the Living Arrangements of Older Persons, 2017.