Trends in sexual activity and demand for and use of modern contraceptive methods in 74 countries: a retrospective analysis of nationally representative surveys oleh Emma Slaymaker, PhD, Rachel H Scott, PhD, Melissa J Palmer, PhD, Luigi Palla, PhD, Milly Marston, PhD, Lianne Gonsalves, MPH, Lale Say, MD, Kaye Wellings, FAcSS