‘Increase by’ controls the means of increasing.

The investment coefficients are related to the coefficients of production in the following way.5 In producing a unit of the jth sector's output (per year) an amount ai; of the ith sector's output is used up in the process (per year). An additional amount of asj must be used up next year if next year's output is to increase by one unit. The stock of the means of production must increase accordingly. The needed increase in stock, i.e., investment, depends on the rate of use-up of the means of production. Let, for instance, the means of production (e.g., machines, buildings, or other equipment), in which the output of the ith sector is embodied in the jth sector, last for 10 years and their rate of use-up be uniformly 1/10 per year. Then in order to increase the use-up of each year by aij, a stock of additional means of production equal to 1 0ai must be provided. Thus, bi1 lOaij. In view of the durable character of the means of production, it is not possible to provide less, for then the use-up could not be kept up at as; per year.