A correlated set of iron type golf clubs is designed to improve performance. The set of clubs includes a plurality of iron type golf clubs having linearly spaced lofts such that a first iron type golf club has a loft which is x degrees greater than the loft of a second iron type golf club and the second iron type golf club has a loft which is x degrees greater than a third iron type golf club and subsequent iron type golf clubs increase in loft at the same rate. The plurality of iron type golf clubs also have lengths which are linearly spaced such that a first iron type golf club has a length which is y inches less than the length of the second iron type golf club and the second iron type golf club has a length which is y inches less than the length of the third iron type golf club and subsequent iron type golf clubs decrease in length at the same rate. The set of iron type golf clubs is further designed such that the design efficiency increases as the loft of the golf clubs decreases.