Fifty-year-old John Gadsby is alarmed by the decline of his hometown, Branton Hills, and rallies the city's young people to form an "Organization of Youth" to build civic spirit and improve living standards. Gadsby and his youthful army, despite some opposition, transform Branton Hills from a stagnant municipality into a bustling, thriving city. Toward the end of the book the members of Gadsby's organization receive diplomas in honor of their work. Gadsby becomes mayor and helps increase Branton Hills' population from 2,000 to 60,000.
The story begins around 1906 and continues through World War I, Prohibition, and President Warren G. Harding's administration. Gadsby is divided into two parts. The first part (about a quarter of the book's total length) is strictly a history of the city of Branton Hills and John Gadsby's place in it. The second part of the book devotes more time to fleshing out the rest of the town's characters.
The novel is written from the point of view of an anonymous narrator, who continually complains about his poor writing skills and often uses circumlocution. "Now, naturally, in writing such a story as this, with its conditions as laid down in its Introduction, it is not surprising that an occasional "rough spot" in composition is found", the narrator says. "So I trust that a critical public will hold constantly in mind that I am voluntarily avoiding words containing that symbol which is, by far, of most common inclusion in writing our Anglo-Saxon as it is, today".

Question: How much did Branton Hills population increase?
Answer: More than 20x.
Alternative answer: 40,000