An estimate of the size of the future population, whether in total or by component parts, is essential information in any planning exercise (RPS, 2005). Population projection is the computation of future changes in population numbers, given certain assumptions about future trends in the rates of fertility, mortality, and migration. Demographers often publish high, medium, and low projections of the same population based on different assumptions of how these rates will change in the future. In the case of the City of Santa Rosa, the city used the medium assumption in projecting population.
Figure 5-2 presents the population projection from 2015 to 2040 in the City of Santa Rosa. The estimated total population for the province of Laguna for the year 2005 was computed using linear interpolation with the population from the 2000 Census of Population and Household (CPH) as base population and population from the 2010 CPH as end population. Linear interpolation was also used to estimate the population of the province for years 2015 to 2040 with the 2010 CPH count as base population, and the 2040 projected population from the 2000 Census-based population projections as end population. The percentage of population of the City of Santa Rosa to that of the Province of Laguna from the 2010 CPH was used to estimate the population of the city for years 2015 to 2040.
Among the 18 barangays comprising the City of Santa Rosa, the most populous barangay is Brgy. Pooc with an estimated 2015 population of 35,091 and a projected 2040 population of 42,656 (11.78 percent) (Table 5-2). The population boom in the barangay is explained by the establishment of Southville Subdivision (Phase 1-9) - a mass housing project of the National Government for informal settlers in Metro Manila.
The next most populated brangays are: Brgy. Dila (9.51), Brgy. Malitlit (7.81 percent), Brgy. Dita (7.24 percent), and Tagapo (7.23 percent).
The least populated is Brgy. Sto.Domingo, with a 1.12 percent share to the projected total population of Santa Rosa. First class subdivisions and a well-organized community are located in this barangay. Other less populated barangays are Brgy. Kanluran (1.52 percent), Brgy. Ibaba (1 59 percent), and Brgy. Malusak (1.85 percent).