Econometric studies based on the so-called q theory have so far been often unsuccessful. One of the main reasons for this seems to exist in the way the average
q (denoted by
qA) is estimated. The
q theory itself, until now, has provided no specific expressions for the
qA. As a proxy for this, some financial and other vague variables such as stock prices have been adopted in prior econometric analyses. The present paper demonstrates the significance of the
qA in our econometric analysis.
Our findings are as follows.
1. A new interpretation of the
qA is obtained along with a new formulation of its microeconomics foundations, namely the
qA is the ratio of Net Cash Flow to the adjustment cost of investment. Utilizing our definition of the
qA, within the confines of the model, we show this value to be determined by such variables as profit rates and investment rates except for the discount rate. We can thus obtain the
qA in a consistent manner with the model.
2. The marginal
q being equal to unity or not is of no relevance to the criterion for an investment decision making and we derive a new investment decision rule from the
q theory. In particular, the optimal investment behavior at any time is to invest so as to maintain the maximal value of the
qA, namely so as to maximize the ratio of Net Cash Flow to the adjustment cost of investment.
3. By estimating the
q values for Japan, United States, Korea and Taiwan, and by attempting a comparative analysis of investment conditions and rationality of investment behavior of these conutries, we find the following in particular:
(a) Throughout the sample periods, from 1970 to 1991, while the
qA values for both Japan and United States are more decreasing than increasing those for Korea and Taiwan are increasing. This means that for Japan and The United States the investment conditions are getting worse, contrary to those for Korea and Taiwan that are improving. Especially, the damage to Japan and the United States from the first oil crisis was more serious than it was to Korea and Taiwan, although the investment conditions thereafter have become similar and competitive among these nations.
(b) Japan and the United States do not show a tendency to follow optimal paths implied by our investment criterion or decision rule, implying instead their investment behavior not fully rational. In contrast, there was a positive correlation between the investment level and the direction of changes in the investment conditions of Korea and Taiwan. Thus their investment behaviors were apparently rational.
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