Siaya County is one of the six counties in Nyanza region. It has a land surface area of approximately 2,530 km² and a water surface area of approximately 1,005 km2. It borders Busia County to the North West, Vihiga and Kakamega counties to the North East, Kisumu County to the South East and Homa Bay County across the Winam Gulf to the South. The water surface area forms part of Lake Victoria (the third-largest freshwater lake in the world). The County consists of six sub-counties and thirty wards. Alego Usonga, Bondo and Gem sub-counties have six wards each; Rarieda, Ugenya, and Ugunja sub-counties have five, four and three wards respectively. Of the six sub-counties, Alego Usonga is the largest with an approximate area of 605.8 km2 while Ugunja is the smallest with an approximate area of 200.9 km2.

Population size and composition

Population size, structure and distribution against the county resource endowment are major challenges to the setting of priorities for development and in implementing plans. In 2009, the population of the county was 842,304 consisting of 398,986 males and 443,318 females. This figure was projected to increase to 1,027,795 consisting of 488,077 males and 539,718 females in 2018. The population has been further projected to rise to 1,114,735 comprising 529,646 males and 585,088 females and 1,285,971 comprising 610,179 males and 675,792 females in 2022 and 2030 respectively. The population of the county is dominated by females at 53 percent against 47 percent males due to a high mortality rate for males between ages 0 years to 19 years and high life expectancy for females. The rapidly increasing population requires increased investments in basic social infrastructure and utilities such as schools, health facilities, water, sanitation, and services.

Child Dependency Ratio

Under 1 year: The population of children under1 year is estimated at 34,905 (17,588 males and 17,317 females) in 2018 and accounts for 3.6 per cent of the total population. This population is vulnerable to preventable illnesses hence specific health interventions should be focused on immunization, nutrition and dietetics and provision of Long Lasting Insecticides Treated Nets (LLTINs) to reduce high incidences of morbidity and mortality. Under 5 years: The population which includes pre-primary school age group (children between 3- 5years) is estimated at 165,619 (83,160 males and 82,460 females) in 2018 and accounts for 16.9 percent of the total population.

Primary School Going (6-13 years): The population of the primary school age group is estimated at 220,334 (111,334 males and 109,000 females) in 2018 accounting for 22.4 percent of the total population. This population also requires targeted interventions on sanitation, nutrition, and reproductive health and can serve as important change agents for the adoption of healthy behavioral practices within the community.

Secondary School Going (14-17 Years): The population of secondary school age group is estimated at 98,324 (49,524 males and 48,800 females) in 2018 accounting for 10.0 percent of the total population. The population of this group is projected to increase to 105,243 (53,009 males and 52,234 females) and 120,575 (60,731 males and 59,844 females) persons in 2022 and 2030 respectively. This population calls for continued investment in socioeconomic infrastructures like schools, training institutions and a strategy to ensure high retention and transition rates to colleges. There is also a need to increase the number of sports and recreational facilities to engage youth in sports and various recreational activities. In addition, this group is most affected by HIV and AIDS in the county. This calls for specific interventions aimed at addressing the scourge.

Child Population

The infant population is projected at 20,713 in 2017 representing 2.4 percent of the total county population. The under 5 years in the County have 154,651 children who are below five years old. This is about 18 per cent of the total population. Primary School Age Group (6-13) in the county, there are 239,035 children who are within the primary school going age. Of this, 54.9 per cent are boys while 45.1 per cent are girls. There will be need to put up more primary schools and employ more teachers to cater for the growing number of the school going children. The primary school enrollment is however low for both genders but worse for the girl child. There is, therefore need to carry out enrollment drives throughout the county. In addition, a programmes on the provision of sanitary towels need to be enhanced to retain the girl child in school.

The Gender Inequality Index (GII)

This is the number of children aged 0-14 relative to the number of people aged 15-64 years. The county‘s child dependency ratio is 90 dependent children for every 100 working-age people. The number of children determines the demand for schools, health care, and other services and is important for effective planning for investment in education and training, recreation and social development. According to a report by Population Action International, 2014, Siaya Human Development Index is estimated to be at 0.46 against the national average of 0.56. National life expectancy is 62.2 and expected years of schooling 11.1. Despite progress in human development at the global, regional and national levels, uneven income distribution and human deprivations persist. This is one of the driving forces behind the new constitutional dispensation in Kenya in which national and county governments coexist to address the emerging inequalities and marginalization