Housing shortage occurs when there is insufficient housing supply to meet the demand from a population in an area. Major cities experiencing housing shortages include Manila, New York City, Los Angeles, Mumbai, Beijing, Kigali, and Cairo. Housing shortages can result from rapid population growth, migration, high birth rates, competing land uses, and limited land supply. Consequences include environmental pollution, homelessness, low health standards, and vulnerability to natural disasters from overcrowded slum conditions. Potential solutions involve slum upgrading and providing more public housing.