Barangay Bia-o

Barangay Bia-o forms part of Santa Maria, a municipality in Ilocos Sur, and is classified as a small barangay.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay Bia-o had a population of 532. This made it the 27th largest of 33 barangays in Santa Maria by population, placing it among the smaller barangays of the municipality. Residents of Barangay Bia-o accounted for approximately 1.77% of the total population of Santa Maria, which stood at 30,006 in the same census year.

Census comparisons between 2015 and 2020 show Barangay Bia-o moving from 577 residents to 532 residents, an intercensal change of -7.8%. The trajectory indicates a contracting community. The Philippine Statistics Authority classifies Barangay Bia-o as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

Santa Maria is a municipality comprising 33 barangays, and serves as the governing unit directly responsible for local services in Barangay Bia-o, including public health, sanitation, peace and order, and civil registration. Within the wider province of Ilocos Sur, which contains 768 barangays across its component cities and municipalities, Barangay Bia-o ranks 558th by 2020 population. Ilocos Sur is classified as a 1st by the Bureau of Local Government Finance, a category that reflects the province's annual regular income.

Like every Philippine barangay, Barangay Bia-o is led by an elected Punong Barangay (barangay captain) supported by seven Sangguniang Barangay members (kagawads), an SK Chairperson, a Barangay Secretary, and a Barangay Treasurer. The next Barangay and Sangguniang Kabataan Elections (BSKE) are scheduled for Monday, November 2, 2026, with officials serving four-year terms under Republic Act No. 12232.