National Adult Literacy Database

This document offers a guide, chronologically arranged, to theories about readability.

The author begins in 1893 with the work of L.A. Sherman on the analytics of literature and continues up to 1948 with the Dale-Chall readability formula and Rudolph Flesch’s work on reading ease.

The author also describes other milestones, including the contributions of psychologists Harry D. Kitson and Edward L. Thorndike; the development of the Winnetka formula for predicting text difficulty by grade level; and the work of William S. Gray and Bernice Leary on what makes a book readable.