 Rather than releasing supplemental editions or volumes, new printings would be made every year with only enough copies made to cover the sales for that year.An analysis of the "Britannica's" articles suggested that roughly 75% required only occasional revising, whereas 25% required revision every 1–3 years.The articles were therefore divided into 30 classifications and a schedule for their revision worked out, such that every article would be checked at least twice a decade.