[The choice of development period and consequent introduction time for a single innovation by an expected profit maximizing firm operating under conditions of rivalrous competition is studied. Factors taken into account by the firm are the increasing cost with compression of the development period, the reduction of profit opportunities with prolongation of the development period, and the probability of rival innovation and imitation which affect the potential rewards available to the firm. Comparisons is made with the timing that would be selected in the absence of rivalry. The effects of intense rivalry are also examined.]

The technique of partial aggregation is explored as a means of preserving the confidentiality of data while enabling research scholars to utilize the information for analytic purposes. For this purpose, two criteria are developed for evaluating the analytic consequences of partial aggregation: One measure indicates the degree of divergence or non-conformity between estimates produced by unaggregated data and partially aggregated data; and the other measure pertains to efficiency loss and expresses the fraction of the useful information in the unaggregated data which remains after the data have been grouped or partially aggregated. These measures are then applied in an experimental test using data from the Call Reports and the Income and Dividend Statements of nearly 5400 member banks of the Federal Reserve System. This experiment consists of evaluating the effect on twenty different regression models of three different levels of aggregation and seven different rules for arraying the data prior to aggregation.

In classical analysis, there is a vast difference between the class of problems that may be handled by means of the methods of calculus and the class of problems requiring combinatorial techniques.With the advent of the digital computer, the distinction begins to blur, and with the increasing emphasis on problems involving optimization over structures, tIlE' distinction vanishes.What is necessary for the analytic and computational treatment of significant questions arising in modern control theory, mathematical economics, scheduling theory, operations research, bioengineering, and so forth is a new and more flexible mathematical theory which subsumes both the cla8sical continuous and discrete t 19orithms.The work by HAMMER (IVANESCU) and RUDEANU on Boolean methods represents an important step in this dnectlOn, and it is thus a great pleasure to welcome it into print.It will certainly stimulate a great deal of additional research in both theory and application.