Four weeks after the four National Book Awards winners were announced, the scope of the awards' influence on sales is starting to take shape. All four winners have experienced sales spikes, but just how much?

Fiction winner Louise Erdrich's The Round House (Harper) sold 30,000 of its 47,000 copies since its victory, according to Nielsen BookScan. In its first week after winning, the book saw a 143% increase at outlets tracked by BookScan, going from 2,000 copies sold to 5,000 copies sold. Since its win, Erdrich's novel has steadily kept increasing in weekly sales, moving 9,000 copies for the week ending December 9.

Katherine Boo's Behind the Beautiful Forevers (Random House), was already a success before it won the Nonfiction award, moving 75,000 copies, but its weekly sales jumped to 1,200 from 300 immediately following its win. Like The Round House, Forevers has steadily increased in weekly sales since the National Book Awards, and last week sold 7,000 copies.

Sales of Poetry winner David Ferry's Bewilderment (University of Chicago Press) have tripled since it won. The collection is now approaching 2,000 copies sold.

S&S/Margaret K. McElderry Books' Goblin Secrets by William Alexander, winner of the Young People's Literature award, had sold 825 copies preceeding its win. Since then, the book has sold 4,500 copies, almost 2,000 of which were in the week ending December 9 – its best week by far – according to BookScan.