TULSA , Okla.

TODD RUTHERFORD was 7 years old when he first understood the nature of supply and demand. He was with a bunch of other boys, one of whom showed off a copy of Playboy to giggles and intense interest. Todd bought the magazine for $5, tore out the racy pictures and resold them to his chums for a buck apiece. He made $20 before his father shut him down a few hours later. A few years ago, Mr. Rutherford, then in his mid-30s, had another flash of illumination

The Educational Development Corp., which announced today that it is pulling all of its titles from Amazon, plans to increase its sales by abandoning the major online retailer, according to the company’s CEO.

Amazon accounted for about 13% of EDC’s sales in 2011, estimated Randall White, CEO of the publicly traded Tulsa, Okla.-based children’s book publisher. The exact number is uncertain because EDC sells to Amazon through distributors who also sell through other channels and do not provide EDC an exact breakdown of sales.