Trends in contraceptive prevalence rates in sub-Saharan Africa since the 2012 London Summit on Family Planning: results from repeated cross-sectional surveys Autor Saifuddin Ahmed, ProfPhD, Yoonjoung Choi, DrPH, Jose G Rimon, MA, Souleymane Alzouma, DESS, Peter Gichangi, PhD, Georges Guiella, PhD, Patrick Kayembe, PhD, Simon P Kibira, PhD, Fredrick Makumbi, PhD, Funmilola OlaOlorun, PhD, Elizabeth Omoluabi, PhD, Easmon Otupiri, PhD, Sani Oumarou, DESS, Assefa Seme, MD, Solomon Shiferaw, PhD, Philip Anglewicz, PhD, Scott Radloff, PhD, Amy Tsui, PhD