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This study aims to investigate Nakajima Aircraft Company's airframe business and its production efficiency during WW II in comparison with Mitsubishi Heavy Industries.

During the Pacific War, Japanese aircraft production was essentially based on job shop system for parts fabrication and sub-assembly. Nakajima Aircraft Company the largest aircraft manufacturer of war-time Japan and Mitsubishi Heavy Industries the second largest utilized both job shop and production line systems for their airframe final assembly lines depending on each plant situations. The United States Strategic Bombing Survey reports evaluated that Nakajima's airframe production system was more developed than that of Mitsubishi, which adhered to original, old-fashioned job shop system. This was substantiated from the fact that Nakajima expanded its production by 1944 to more than eight times of its 1941 production, and Mitsubishi produced only three times for the same period.

However, in production efficiency measured by airframe weight produced per month per employee, Mitsubishi was predominant until August to October 1944. A positive correlation was observed between production efficiency and monthly number of airframe production. Mitsubishi's improvement degree of production efficiency agreed well with the estimation by learning curve theory, but Nakajima's improvement of production efficiency far exceeded the estimation. This is considered to be the effect that Nakajima's labor utilization rate, which was approximately half of that of Mitsubishi in September 1943, might have increased rapidly as the monthly airframe production increased. The difference of the final assembly line did not have decisive influence on the production efficiency, but the increase in the number of monthly airframe production was influential.

The production efficiency continuously increased as the monthly airframe production increased, and then dropped sharply from the end of 1944 and after due to the rapid decline of monthly production, which was caused by shortages of essential materials and engines, US air raids from November 1944 and after, factory evacuation, and labor shortage.

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Using longitudinal micro data for Mitsubishi Shipbuilding employees from 1918 to 1946, this paper quantitatively analyzes the promotion and selection process for white-collar workers during the prewar period. Previous studies on the postwar period have mostly examined this career pattern quantitatively, while historical studies focusing on the prewar period are mostly qualitative. Moreover, even the few quantitative studies on the prewar period do not employ such methods as career trees and event history analysis, which are generally used in the studies focusing on the postwar period. Therefore, the main purpose of this paper is to investigate the career pattern of white-collar employees in prewar Japan in a quantitative way comparable with studies focusing on postwar Japan.

We target two cohorts of white-collar workers—those who joined Mitsubishi Shipbuilding in 1918 and 1921—and track their careers (section and position) until 1946 by matching three internal data sources, including lists of personnel. We first draw up the career trees of new white-collar employees in both cohorts to illustrate the characteristics of their career patterns. Next, we employ event history analysis to test the differences in the career patterns between sub-groups, such as clerks and engineers. Finally, we estimate a logit model to determine the factors of their “survival” until 1939. We find that (1) the speed of promotion differs considerably across white-collar workers in the same cohort, (2) “return match” is observed not only in promotion to section manager positions but also in promotion to division manager positions, (3) despite a high ratio of resignation, most remaining white-collar workers are promoted to division managers, and (4) engineers are more likely than clerks to stay with the company for more than 20 years. Findings (1) to (3) are common to the career patterns of white-collar workers in the prewar core banks of Zaibatsu groups but contrast with those of large postwar firms.

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