Estimates and Future Projections of Demography

The projected population at the start of the planning period in 2018 is 59,658. Assuming a constant annual growth of 1.72%, the projected population in 2028 is 70,835. There are 12,613 projected number of households in 2018 which will grow to 14,976 in 2028. Urban population is projected to be 15,150 in 2018 and 17,988 in 2028. The number of people living in the rural barangays will increase from 44,508 in 2018 to 52,847 by 2028. The doubling time, or the time required for Irosin’s population to double itself given the present fixed growth rate of 1.72% is 40 years. (Refer to Table DE-11)

By 2018, the school age going population is projected to be 27,003 and will be 32,098 in 2028. Population of elementary and secondary level school age will be 10,206 and 9,842 in 2028 respectively. Dependent population will reach 29,171 in 2028 with 25,420 young dependents 0 to 14 years old and 3,750 old dependents 65 years and over. The projected population of the labor force 15 years and over in 2018 is 38,108 and 45,247 in 2028. (Refer to Table DE-12)

Population Change

Historical Growth of Population

Irosin’s population has grown from 8,644 in 1903 to 56,662 in 2015 with a cumulative increase of 48,081 or 556%. In this 112 years period, the average growth rate of the population is 1.68% per year. From the first census in 1903 to 1918, the population grew by 3.39% annually. There was a sharp decline in growth in the period 1918 to 1939 that rebounded back up to 1.79% annually by 1980. From 1980, there was again a decline to 1990 and increasing trend up to 2.23% by 2000. There is a decreasing trend in annual population growth rate from a high of 3.39% in the period 1903 to 1918 to the present 1.72% for 2010 to 2015. Historically, the growth rate of Irosin is lower than the national and provincial growth rate. For 2000 to 2010 period, Irosin’s annual growth rate of 1.29% is lower than the national growth of 1.90%, the regional growth of 1.46%, and the provincial growth rate of 1.31%. (Refer to Table DE-6)


Fertility and Mortality

The simplest and most commonly used index of fertility is the Crude Birth Rate (CBR) which is the number of births divided by population expressed in thousands. In 2016, the CBR of the municipality is 21 or 23 live births per 1,000 of population. The local trend in CBR fluctuates during the last five years but is generally on the range of 20 to 25 and fertility is generally decreasing. Mortality or the occurrence of death is roughly measured by the Crude Death Rate (CDR) which is the number of deaths per 1,000 of population. The 2016 CDR is 6.38 deaths per 1,000 of population. The CDR of Irosin for the past five years ranges from 7.95 to 6.38 and mortality rate is generally decreasing. Irosin’s CBR in 2013 is 22.6 which is lower than the national CBR of 24.4 in the same year. For CDR, the national rate is 6.52 in 2016 which is higher than the local CDR of 6.38. (Refer to Table DE-7)

The average rate of natural increase (RNI) in population, which is the difference between CBR and CDR, is 1.47% for the past five years. Since the population growth rate is higher than the rate of natural increase, the population is not closed and it is assumed that 0.25% of the growth rate is net of in-migration and out-migration.


Other Population Characteristics

Labor Force Population and Employment

The labor force population, or those 15 years and over, is 36,194 or 64% of the total population in 2015. Of these, 52% are employed while 48% are not employed . Of all males 15 years and above, 73% are employed while only 30% are female. The provincial employment rate is at 56%. The local unemployment rate in 2013 is 17.9% . Of the 18,646 gainfully employed population, 28% are laborers and unskilled worker, 22% are skilled agricultural workers, 15% are service and sales workers, 8% are craft and related trades workers. (Refer to Table DE-9)


Literacy, Educational Attainment and Attendance to School

In 2015, 99% of Irosin’s population ten years old and over is literate, with both males and females at 99% literacy. The provincial literacy rate is also at 99%. Of the 5 years old and over population of 49, 801, 38.9% are in elementary grade level, 39% at high school level, 14.1% are elementary graduate, 21.5% are high school graduate, 7.4% are college undergraduate, 7.9% are academic degree holder while only 0.1% has post baccalaureate education. There are more female academic degree holders than male with a ratio of 73 males for every 100 females. Of the 24,872 with ages 5 to 24 years old, only 74% are attending school. The school participation rate for 7 to 12 years old is estimated to be 97% and only 78% for ages 13 to 18 years old. There are more males attending school at 104 male to female ratio. (Refer to Table DE-8)


Marital Status, Household Size and Religions Affiliations

The marital status of the 43,102 ten years old and over population is 48.1% single, 34.6% married, 11.1% common law/live-in, and 5.1% widowed 5.1%. There are more single males with 122 male to 100 female ratio. The sex ratio for those with married status is 96 males per 100 male. Half of those 20 years old and over is married, 25.8% are single, 7.4% are widowed, 1.5% is divorced/separated and 15.3% is common-law/live-in. Of the population below 20 years old, 98% are single.

Of the PSA enumerated 11,418 households in 2015, 38% are with 5 to 7 members, 31% with 3 to 4, 16% with 1 to 2 members and there are 15% or 1,693 households with 8 and above members. The PSA average household size is 5.0.

The religious affiliation of Sorsogon province population is predominantly Christian, with 94.29% Roman Catholic, 1.77% Iglesia ni Cristo and the rest are distributed in other religious affiliation. Language spoken at home in Sorsogon province in 2010 is 98.9% Bikol, 0.9% Tagalog, 0.1% Bisaya and 0.1% Maranao.

Population Distribution

Urban and Rural Population

The 2015 urban population is 14,839 or 25% of the total population while the rural population is 42,273 or 75% of the total population. Households distribution is 26% or 3,113 are in urban barangays and 74% or 8,865 are in rural barangays. The most populated barangay is the urban barangay of Bacolod with a population of 4,518. Among the contributory factors leading to the high population of Bacolod is its proximity to town center or the central business district (CBD), the high density of housing units and the presence of informal settlers in the river control dike and at riverbanks. The second most populous barangay is the rural barangay of Monbon with a population of 4,414. Monbon’s population growth is attributable to its location being alongside the national highway and relative proximity to town center, its vast coconut lands in moderately level slopes which are also used for residential purposes, and the presence of tourism establishments. Gabao, a rural barangay with a population of 4,286, is the third most populous barangay. Gabao is strategically located at the center of a catchment area covering the barangays of Bulawan, Tongdol, Gumapia and Gulang-gulang. The barangay is a nodal growth center in the area and with a growing commercial hub. The urban barangay of San Pedro is the fourth most populous barangay with 3,154 population. San Pedro is the largest in terms of land area among the urban barangays, contains part of the CBD, is traversed by the national highway and the site of major institutions. (Refer to Table DE-3)


Urbanization Level

There is a declining urbanization level, or growth in the proportion of population living in urban barangays, in the past 25 years. In 1980, 36% of the population are living in the urban area and the proportion dropped to 31% in 1990, to 27% in 2000, 26% in 2010, and to 25% in 2015. This declining trend is correlated to the disparity in the population growth rate of rural and urban barangays. The annual growth rate of urban barangays from 1995 to 2015 ranged from 0.34% to 1.15%, while the rural barangay’s growth rate ranged from 1.41% to 2.98% in the same period. The main factor contributory to this trend is the constraint on the availability of land for expansion of built-up areas in the urban barangays. The urban densities of San Julian, San Juan, San Agustin and Bacolod are at its highest. The expansion of built-up areas in San Pedro, which has a large land are, is constrained by the presence of irrigated rice lands. In comparison, 14 % of Sorsogon’s population lives in urban barangays in 2015. (Refer to Table DE-4)


Population Density and Built-Up Density

Irosin’s gross population density is 375 persons per square kilometer or 3.75 persons per hectare in 2015. Urban density is at 45 persons per hectare compared to rural density of 2.86. The highest population density is found in urban barangays of Bacolod with 246 persons per hectare, followed by San Juan at 205, San Agustin and San Julian at 140, and San Pedro at 12. The densest rural barangay is Gabao with 11 persons per hectare, followed by Gulang-gulang and Macawayan at 9. Rural barangays with lowest population density is Cawayan with less than one person per hectare, followed by Cogon, Liang, Mapaso and Tabon-tabon with only 1 person per hectare population. The population density of rural barangays is significantly lower since habitation areas are usually clustered on small areas surrounded by vast agricultural lands. Irosin’s gross population density is slightly higher compared to Sorsogon province’s 3.74 persons per hectare. (Refer to Table DE-5)


Hierarchy of Settlements

Barangay San Julian ranks first in the hierarchy of barangays as it is the seat of municipal government, the public market, the Catholic parish church, the public auditorium and majority of the commercial establishments of the CBD. While Bacolod maybe the most populous and densest barangay, it is considered as second in the hierarchy considering that the existing built-up use of the barangay is predominantly residential. Barangay San Juan and San Pedro are third in the hierarchy based on population density and significant presence of institutional and commercial establishments in the area. San Agustin is fourth in the hierarchy based on its population density.

Gabao is the fifth based on its population, population density and the built-up density. Gabao is the main nodal growth center in the west quadrant of the municipality and has the highest area of built-up land uses outside of the urban barangays. Monbon which is the most populous rural barangay ranks sixth in the hierarchy. Monbon is also a growth center for tourism and has significant built-up area. The barangay of Patag occupies the seventh rank in the hierarchy of settlements based on its population and its role as the nodal growth center in the eastern quadrant.

Population Composition

Population and Households

The population of Irosin as of August 1, 2015 was 56,662 based on the 2015 PSA Census of Population. Irosin’s population is higher by 4,885 compared with the population of 51,777 in 2010, and by 11,155 compared with the population of 45,507 in 2000. The rate at which the population grew during the period 2010 to 2015 was 1.72%. Irosin’s population accounted for 7.15% of Sorsogon province total population of 792,949 and ranked sixth in terms of number of population. There are 11,978 documented households in the same year and the average household size is 4.73. The population for the year 2018 is projected to be 59,658 and the number of households is 12,613.


Population Composition

Irosin’s population is expansive, that is, a very large proportion of population belongs to the younger age group. In 2015, the age group below one-year to 14 years old accounted for 36.12% of the total population. This kind of population structure is brought about by high fertility since new births are naturally added to lower age group. There is a trend of decreasing fertility as the proportion of age group below 14 years old declined from 44% of the local population in 1990, to 42% in 2000, and to 39% in 2010. The productive population with ages ranging from 15 to 64 years old comprise 59.58% of the total population in 2015, from 54% in 2000 and 56% in 2010. In comparison with national data, the proportion of productive age is 62% of the total population in 2010. Senior citizens accounted for 7.95% of the local population. (Refer to Table DE-1 and DE-2).

Male population is slightly higher than the female population during the census year 2010 and 2015. There are 103 males for every 100 females. The local age-sex distribution follows a worldwide pattern in which males predominate at birth but the ratio gradually declines with increasing age presumably because males have higher age-specific mortality rates. Consequently, females tend to outnumber males as their age advances. For the age group 65 and above, the ratio is 64 males for every 100 females in 2015.

There is a high total dependency ratio, or the ratio of those who are too young (below 15 years old) and too old (65 years and above), to those who are 15 to 64 years, is 70 dependents and for every 100 productive individuals in 2015. The young dependency ratio is 61 young dependents for every 100 productive individuals while the elderly dependency ratio is 9 out of 100. Local total dependency ratio is declining from 92:100 in 1990, to 85:100 in 2000 and to 78:100 in 2010. About 58.58% of the total population are in the working age of 15 to 64 years old, with a male to female ratio of 104. The proportion of those in the working age is increasing from 52% of the population in 1990, to 54% in 2000 and 56% in 2010. Comparing to national data, 62% of the Philippine population in 2010 are in working age. Almost half of the population or 45% are in the school-going age of three to 22 years old. In pre-school age (3 to 6 years) are 9.58% of the population, 14.41% are in elementary school age (7 to 12 years), 13.89% are in secondary school age (13 to 18 years) and 7.43% are in tertiary school age (17 to 22 years).