The quality and usefulness of an index of industrial production depends upon the raw data used and the methodology followed. This chapter discusses the availability and quality of the basic production and other related statistics used. A number of private trade associations and research organizations also made valuable contributions in building China's statistical information system. Data on Manchurian industries are not as readily available, as one would expect. It is true that the South Manchuria Railway Company conducted painstaking surveys of the area and published its findings in literally thousands of volumes of documented materials. The cotton yarn data are relatively complete and continuous, but data for many consist of estimates representing the research results of a number of experts. During the war years, data for the Free China are the best among all regional data. Manchurian data during the war are scattered and incomplete, and there is almost no economic information about the other Japanese-occupied regions.