Hiroki Murakami

A Non-Walrasian Microeconomic Foundation of the “Profit Principle” of Investment

In this chapter, microeconomic foundation of the “profit principle” of investment is discussed from a non-Walrasian/Keynesian perspective. A non-Walrasian “quantity constraint” is introduced in the intertemporal profit maximization problem to consider non-Walrasian/Keynesian excess supply situations. Consequently, we find that it is possible to provide microeconomic foundation for the profit principle in the case of static expectations but it may not in the case of more general types of expectations. We also clarify that Tobin’s q can also be defined in non-Walrasian/Keynesian excess supply situations.

Identification of types of obstacles for mobile robots

For service robots coexisting with humans, both safety and working efficiency are very important. In order for robots to avoid collisions with surrounding obstacles, the robots must recognize obstacles around them. In dynamic environments, not only currently moving obstacles but also movable obstacles should be recognized. In this paper, three types of obstacles, such as stationary, movable and moving, are defined, and a method to identify the type of obstacles is proposed. The experiments using a mobile robot were conducted to evaluate the usefulness of the method.

A two-sector Keynesian model of business cycles

In this paper, we examine the effect of sectoral interactions on business cycles in a simple Keynesian model. As a first step for introducing viewpoints of multiple sectors in the context of business cycles, we consider a dual economy in which there are only two kinds of goods: the consumption good and the investment good. By examining a two†sector Keynesian model, we intend to take a look at some phenomena induced by interactions between the consumption good sector and the investment good sector, which cannot be observed in one†sector models. We then find that the stability of equilibrium and the possibility of emergence of a periodic orbit depend on whether the Keynesian stability condition holds or not and that along periodic orbits (business cycles), the consumption good sector lags behind the investment good sector and that the volatility (measured by the ratio of the amplitude of cycles to the equilibrium value) of the investment sector is larger than that of the consumption good sector. Also, we supplement the analysis by performing numerical simulations.

Time elements and oscillatory fluctuations in the Keynesian macroeconomic system

Abstract In this paper, we discuss the relationship between three time lags (the consumption lag, the investment decision lag and the gestation lag) and oscillatory economic fluctuations in the Keynesian IS-LM system. We first confirm that in the absence of time lags, the monotone convergence to the unique equilibrium is observed. Next, we demonstrate that, in the Keynesian IS-LM system, in the existence of the investment decision lag and the gestation lag, oscillatory fluctuations are generated around the equilibrium if the gestation lag is relatively long, while in the existence of the consumption lag and the gestation lag, oscillatory behaviors may not occur. We then conclude that the existence of time lags may be one of the major causes of oscillatory fluctuations.

Economic growth with demand saturation and “endogenous” demand creation

In this article, we present a model of economic growth through “demand creation” in the face of “demand saturation,” by representing demand saturation by an S-shaped logistic function and reckoning the firms R&D as an activity to determine the probability of product innovation, that is, of demand creation. By defining the parameter of birth rate of a new product as the probability that a new product is derived from an existing one and identifying the time path of this parameter with the firms R&D plan, we derive the optimal R&D plan and examine the growth rate of the firms expected total revenue along this optimal plan. We then find that the optimal birth rate of a new product is influenced positively by the speed of diffusion of demand and the initial level of demand but negatively by the unit cost of production and the interest rate and that the growth rate of the firm converges to the optimal birth rate of a new product.

A note on the “unique” business cycle in the Keynesian theory

In this paper, we explore the existence and “uniqueness” of a limit cycle in the Keynesian theory. In a model with the simplest (linear) Keynesian consumption function and the logistic investment function based upon the profit principle, we establish the existence of a periodic orbit (irrespective of the speed of quantity adjustment) and, with the help of the theory on generalized Lienard systems, verify the uniqueness of it for the case in which the speed of quantity adjustment is large enough.