The U.S. government estimates the total population at 11.6 million (midyear 2019 estimate). According to a December 2018 survey conducted by GESIS-Leibniz Institute for the Social Sciences, 57.1 percent is Roman Catholic, 2.3 percent Protestant, 2.8 percent other Christian, 6.8 percent Muslim (mostly Sunni), 0.6 percent Orthodox, 0.3 percent Jewish, 0.3 percent Buddhist, 9.1 percent atheist, 20.2 percent “nonbeliever/agnostic,” and 0.5 percent other. A 2015 study by the Catholic University of Louvain estimates the Muslim portion of the population is 7 percent. According to the study, a plurality of Muslims resides in Flanders (42.2 percent); it estimates 35.5 percent of Muslims reside in Brussels and 22.3 percent in Wallonia. According to Catholic University of Louvain sociologist Jan Hertogen, based on data in the 2015 study, 24.2 percent of the Brussels population and 7.5 percent of the Antwerp population is Muslim.