Japanese and Korean ancestry. Roman Catholicism is the predominant religion, with 85% of the population claiming an affiliation with it.The programmed U.S. military buildup (2010–14) will cause an unprecedented population increase (approximately 40% or nearly 80,000 people at the peak of constructions24 - ) which will significantly impact Guam's very limited and aging infrastructure. This expected population increase would otherwise occur over a 20 year period. The official languages of the island are English and Chamorro.