In 2022, the population of Thayer was 49, a 2.00% decrease year-by-year from 2021. Previously, in 2021, Thayer's population was 50, a decline of 0.00% compared to a population of 50 in 2020.
The median age in Thayer, IA is 31.6, as per 2021 ACS 5-Year Estimates. Of the total population, 29.82% were under the age of 15, 12.28% aged 15 to 29, 56.14% aged 30 to 64, 1.75% aged 65 to 84, and 0.00% were 85 years of age and older.