The population of the province in 2010 was 658,587 persons, registering an increase of 26,332 persons over the 2007 population of 632,255. This figure accounted for 13.87 percent of the region's total population. Among the four provinces in the region, Ilocos Sur has the second lowest population, next to Ilocos Norte. Among the municipalities and component cities of the province, Candon City is the most thickly populated with 57,884 persons. This accounts for 8.8 percent of the total provincial population. On the other hand, Sigay has the least number of persons with 2,419 or 0.37 percent of the provincial population. Sugpon follows with 3,820 persons.