With present wage levels already high, and with organized labor demanding still higher wages for the future, it is necessary for management to secure higher productivity from labor in the future than has been secured in the past. In some cases organized labor has demanded that future wage increases be granted with the understanding that such increases will not be followed by compensating price increases. Wage increases without compensating prices increases can be satisfactorily granted only if the wage increases are accompanied by increased labor productivity. At the present time, such increased productivity cannot be obtained by speeding up the operator to an unreasonable pace. Labor will not tolerate such practices. The increased labor productivity necessary to compensate for wage increases must, therefore, be obtained by the use of more efficient production methods. In some cases, increased productivity is secured by the installation of more efficient machinery and equipment. In other cases, particularly with assembly operations, rearrangement of the stock bins, the installation of simple jigs and fixtures, and the revision of work methods to eliminate unnecessary motions and to increase the efficiency of performing the remaining motions may cause considerable increases in labor productivity without unreasonable speed up. This latter method of increasing efficiency is known by various names, some of the more common of which are motion study, methods engineering, and work simplification.

The average person usually visualizes modern production as performed almost exclusively by large numbers of workers who constantly repeat the same operation for long periods of time. Doctor Ralph M. Barnes, on page 349 of Motion and Time Study (1), points out that such long-run production is not the typical situation even in larger plants. On the other hand, Doctor Barnes states that most operators work on relatively short-run production with frequent work changes. Any method of increasing the productivity of short-run production would, therefore, be applicable to a wide range of industrial effort.

Motion study literature recognizes the fact that, other things being equal, a person tends to perform an operation faster if the work is arranged so that it can be performed by a symmetrical motion path rather than if it is performed by a nonsymmetrical motion path. Small assembly work is usually performed symmetrically by the expedient of arranging the workplace so that each hand builds a complete assembly simultaneously with the other hand.

A hand motion path is said to be symmetrical when it meets two requirements. First, at any point in the cycle the right and left hands are equal distances to the right and left respectively of the center line of the body; to fulfill this requirement, components of motion to the right and left of the center line of the body must be performed by the hands moving simultaneously, in opposite directions, and for equal distances. Secondly, at any point in the cycle the right and left hands are equal distances in front of the body; to fulfill this requirement, components of motion toward or away from the body must be performed by the hands moving simultaneously, in the same direction, and for equal distances.

Several years ago, while the author was employed as a motion study operations which led him to believe that considerably larger time savings could be made by the application of symmetrical motion paths to short-run production, than could be made on long-run production where the worker changed operations infrequently. It appeared that less practice was required to attain a given level of skill if the motion path were symmetrical than if it were nonsymmetrical. Since, as has already been pointed out, short-run production represents a very large proportion of all industrial effort, it appeared profitable to make a study to determine if the application of symmetrical motion paths would actually yield greater savings on short-run production than on long-run production; any methods producing time savings on short-run production would have a wide field of possible applications.

It was the purpose of this study to determine if the impressions mentioned in the preceding paragraph could or could not be verified. An operation was arranged so that it could be performed by either a symmetrical or a nonsymmetrical motion path. Several operators performed short 25-cycle runs of the operation by one motion path and then shifted to the alternate motion path at the end of each 25-cycle run. This procedure was continued until 29 runs by each motion path had been completed by each operator. Such a procedure produced the effect of the operators working on short-term production with frequent changes of operation. All operating times were recorded. A comparison of the time records for the two motion paths gave an index of their relative efficiency. Such comparison did indicate that greater time savings could be expected from the application of symmetrical motion paths to short-run production than by application to long-run production.