The age distribution, , in Flawil is; 1,216 children or 13.0% of the population are between 0 and 9 years old and 1,248 teenagers or 13.4% are between 10 and 19. Of the adult population, 1,209 people or 13.0% of the population are between 20 and 29 years old. 1,514 people or 16.2% are between 30 and 39, 1,279 people or 13.7% are between 40 and 49, and 1,127 people or 12.1% are between 50 and 59. The senior population distribution is 790 people or 8.5% of the population are between 60 and 69 years old, 548 people or 5.9% are between 70 and 79, there are 333 people or 3.6% who are between 80 and 89, and there are 56 people or 0.6% who are between 90 and 99.