"The ferrite predicting diagrams are developed by calculations that use chemical analyses and measured ferrite content@ then correlating composition and ferrite content. Since both composition and ferrite content are measured@ each input data point used in developing the correlation has a degree of uncertainty associated with it. The uncertainty in ferrite measurement and approaches to make it as reproducible as possible were considered in great detail in WRC Bulletin 318. A series of predicting diagrams have been developed using chemical composition and measured ferrite content@ including the Schaeffler Diagram (1949)@ the DeLong Diagram (1973) and the WRC-1988 Diagram. The latter was first published in the Welding Journal in December@ 1988 (hence the name ""WRC-1988 Diagram"") and then was more completely described@ with its supporting data@ in WRC Bulletin 342. Each successive diagram was considered to be an improvement on the preceding diagram@ but the degree of uncertainty in each diagram remained somewhat unknown"