Swanson had a population of 2,241 at the 2018 New Zealand census, an increase of 591 people since the 2013 census, and an increase of 855 people since the 2006 census. There were 699 households. There were 1,104 males and 1,134 females, giving a sex ratio of 0.97 males per female. The median age was 32.6 years, with 504 people aged under 15 years, 507 aged 15 to 29, 1,062 aged 30 to 64, and 168 aged 65 or older. Ethnicities were 62.8% European/Pākehā, 15.1% Māori, 11.2% Pacific peoples, 25.0% Asian, and 2.1% other ethnicities. The proportion of people born overseas was 33.6%, compared with 27.1% nationally. Although some people objected to giving their religion, 50.5% had no religion, 31.5% were Christian, and 12.3% had other religions. Of those at least 15 years old, 450 people had a bachelor or higher degree, and 243 people had no formal qualifications. The median income was $38,700. The employment status of those at least 15 was that 984 people were employed full-time, 231 were part-time, and 54 were unemployed.
The area to the south and west of Swanson, comprising the statistical area of Swanson Rural, had a population of 2,355 at the 2018 New Zealand census, an increase of 225 people since the 2013 census, and an increase of 318 people since the 2006 census. There were 750 households. There were 1,212 males and 1,146 females, giving a sex ratio of 1.06 males per female. The median age was 40.7 years, with 402 people aged under 15 years, 495 aged 15 to 29, 1,176 aged 30 to 64, and 282 aged 65 or older. Ethnicities were 86.9% European/Pākehā, 14.3% Māori, 5.0% Pacific peoples, 7.1% Asian, and 2.5% other ethnicities. The proportion of people born overseas was 24.1%, compared with 27.1% nationally. Although some people objected to giving their religion, 59.5% had no religion, 27.9% were Christian, and 5.1% had other religions. Of those at least 15 years old, 438 people had a bachelor or higher degree, and 261 people had no formal qualifications. The median income was $39,900. The employment status of those at least 15 was that 1,113 people were employed full-time, 309 were part-time, and 57 were unemployed.
