参考：

ティロール：メモ

https://nam-students.blogspot.com/2019/02/tirole-jean-1985-asset-bubbles-and.html

10. CONCLUSION To conclude I believe that the investigation of overlapping generations models should somewhat shift emphasis from the study of money to that of assets that are held for more speculative purposes. It is clear that the models and the empirical evidence are too preliminary to settle the question of whether we should expect to observe asset bubbles in overlapping generations economies. And we have not solved the old debate about which one of overlapping generations and infinitely lived consumers (or overlapping generations with bequests) is the "right" model. The difference between the two formalizations is substantial since bubbles may exist in the former but not in the latter. But I hope to have convinced the reader that in our current state of knowledge we would be best advised to believe that bubbles are not inconsistent with optimizing behavior and general equilibrium.

A good understanding of their definition and properties may be required in various fields such as empirical studies of asset pricing, monetary theory, and welfare economics. Massachusetts Institute of Technology Manuscript received June, 1983; final revision received November, 1984.

31 It can be shown that the maximum rate of growth of an asset consistent with a bubble on this asset is the difference between the asymptotic rate of growth of the economy and the asymptotic rate of interest in the Diamond bubbleless economy. The possibility of future creation is indeed one of the reasons why Tobin [37] is somewhat sceptical about the use of overlapping generations models of money without transaction motives ("There is no governmental commitment to the value of money," p. 85). 32 Potential examples are rare stamps, letters of past famous writers or personalities, famous paintings, gold, diamonds, land. For instance the market fundamental-consumption value-of rare stamps seems to be low-all the more that they generally sit in a bank; but their price can be very high. Artificial and real diamonds cannot be told apart with the naked eye. If there is no snobism effect, their market fundamental is basically the same, in spite of the fact that they command very different prices. If the real value of the asset depends on its price, the analysis is not as clear-cut; it then resembles that for money with transaction motives.

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3 1. Complementarity The most common notion of complementarity is that from standard price theory, where, for example, two inputs are complements if raising the price of one of them lowers the use of the other. Here we adopt a broader conception (due to Edgeworth) that is not dependent on the special structure of prices and quantities and that permits analysis of such complex phenomena as organizational structures and government policies. Specifically, we say that a group of activities are (Edgeworth) complements if doing more of any subset of them increases the returns to doing more of any subset of the remaining activities. In a differentiable framework, this idea corresponds to positive mixed-partial derivatives of some payoff function: the marginal returns to one variable are increasing in the levels of the other variables. However, for many of the problems one wants to address, it is unnatural or extremely restrictive to assume even divisibility of choice variables, let alone smoothness of objective functions. Fortunately, however, those conditions are also unnecessary for analyzing systems of complements. Looking at the informal definition above, we see that Edgeworth complementarity is a matter of order ─ “doing more of one thing increases the returns to doing more of another.” Formally, consideration of choices from sets of objects that are (partially) ordered leads into the branch of mathematics known as lattice theory. The analysis of complementarity then becomes the study of so-called supermodular functions on lattices. We will actually need very little of this formal structure to exposit the key results of this area that are useful for analyzing the questions of complementarity and systems that arise in the study of Japanese economic organization, but some minimal terminology is useful. First, a lattice is just a set X whose elements are (partially) ordered and that has the property that, for any two points x and y in X, X also contains a smallest element under the order that is larger than both x and y and a largest element that is smaller than both. We write x∨y (read “x join y”) to denote the smallest element larger than both x and y, and x∧y (read “x meet y”) to denote the largest element that is smaller than both x and y. Any subset of the real numbers with their natural ordering forms a lattice. A different lattice is obtained by taking the real numbers but reversing the usual order. For a richer example, consider the N-dimensional Euclidean space RN together with the familiar component-wise, product (partial) order, denoted ≥N and given by x ≥N y if and only if xn Figure 1: The set S and the four point set {x,y,x∧y,x∨y} are both sublattices of R2. ≥ yn, n = 1,...,N, where ≥ is the usual order on the real numbers. This is a lattice, and the meet and join operations are given by the component-wise min and max: x∧y = (min{x1,y1},...,min{xN,yN}) and x∨y = (max{x1,y1},..., max{xN,yN}), as in Figure 1. Clearly x∧y is (weakly) smaller than either x

4 or y, and it is the largest point having this property because any higher point is larger in at least one component than one or both of x and y. Similarly, the component-wise maximum, x∨y, is the smallest point that is larger than both x and y. Generally, instead of doing this construction with the product lattice RN obtained from N copies of the lattice R, we could have begun with any N lattices and constructed a new lattice as the N-fold product, with the product, component-wise order. A quite different example is provided by starting with some arbitrary set Z and considering the set 2Z of subsets of Z, with set inclusion defining the partial order: x ≤ y means x ⊂ y. In this context, given any two subsets x and y of Z, x∧y is simply the intersection x∩y, because the intersection is contained in both sets (that is, it is smaller than both in this order) and it is the largest set with that property. Similarly, x∨y is the union x∪y. Besides helping in remembering the meaning of the symbols ∧ and ∨, this example illustrates that the elements of a lattice can be complicated objects. A sublattice of a lattice X is a subset S of X that is closed under the operations of meet and join that are defined in the original lattice, that is, if x and y are each in S, then so are their meet and join. Any lattice is a sublattice of itself. In Figure 1, the set S, the four-point set {x, y, x∧y, x∨y} and the two-point set {x∧y, x∨y} are all sublattices of RN and each of the sets in this list is a sublattice of the preceding ones. Each of the singleton sets is also (trivially) a sublattice. The two-point set {x, y} in the figure is an example of a set that is not a sublattice of R2. Formally, one verifies this by observing that the set does not contain either the meet or the join of x and y. From a modeling perspective, what this means is that starting from the feasible point x, one cannot increase the first component from x1 to y1 without also decreasing the second component. If we think of {x,y} as a constraint set, then the constraint forces the decision maker to choose between high values of the first and second component. Sublattice constraints never restrict a decision maker in that way: Increasing the value of some decision variables never prevents one from increasing the others as well, and, similarly, decreasing some variables never prevents decreasing others. Intuitively, sublattice constraints represent a kind of technical complementarity. For example, a sublattice constraint could be used to model the idea that investing in more flexible equipment and a more broadly trained factory work force never prevents a firm from widening its product line or even that these are a necessary prerequisite for such a change. There is a second element in the formalization of complementarity that is expressed not through the constraints but through the objective function. Given a real-valued function f on a lattice X, we say that f is supermodular and its arguments are (Edgeworth) complements if and only if for any x and y in X, f (x) - f(x∧y) ≤ f(x∨y) - f(y). This is simply a mathematical restatement of the verbal definition given earlier: the returns to increasing some of the variables are greater the larger are the values of the other variables. This is easy to see in the R2 example. There the defining inequality says that the change in f going from the coordinate-wise minimum, x∧y, to x (or y) is less than that associated with the parallel move from y (or x) to the maximum, x∨y (see Figure 1 again): increasing one argument of the function has a bigger impact when the other argument is at a higher level. If f is twice continuously differentiable,

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9 Increasing returns to scale is a source of strategic complementarity in games. Diamond's (1982) macroeconomic search model and the network externality models of Farrell and Saloner (1986) and Katz and Shapiro (1986) provide good illustrations. In these models, the payoff of an individual player j has the form f(Σixi) - C(xj) where f is convex or f(Σi≠jxi)xj - C(xj) where f is increasing. These conditions are usually interpreted as reflecting returns to scale in matching processes, telephone systems, shared technologies, and the like. The key implication is that the mixed partial derivative of the player j's payoff function with respect to xj and any other xi is positive. Moreover, complementarity ─ rather than general returns to scale ─ provides a better descriptive account in such applications. For example, the gains to personal computer users from focusing on just one or two standards is that doing so eases the development of complementary products including both software (operating systems, applications software) and hardware (fax boards, monitors, storage devices). Finally, the equilibria of some supermodular games have clear and strong welfare properties. If each player's payoff is increasing (decreasing) in the choice variables of the other players, then the largest (smallest) equilibrium is Pareto-preferred to any lower (higher) combination of strategies, including any other equilibria. However, if the payoff functions are differentiable, an increase (decrease) in all players' strategies from this equilibrium would generally be Pareto-improving. It is also true that in such games, there is no possibility of a subgroup of players' successfully deviating as a group from the Pareto-preferred equilibrium. This can be formalized as follows. Consider any set of players M and any Nash equilibrium of the induced game where these players select their strategies given that the players not in M adhere to the strategies given by the Pareto-best (that is, the largest or smallest) Nash equilibrium. Then the original Nash equilibrium is Pareto-preferred for the members of M to any other equilibrium in the induced game. The same conclusion holds even if the individual payoffs are not monotone in the other players' strategies so long as the game has a unique equilibrium. 2. Japanese Economic Organization7 Table 1 lists many of the distinctive features of the Japanese pattern of economic organization, as well as some key characteristics of the post-War economic environment in which this system has developed and flourished. Examining these from the perspective of complementarity reveals important interactions and systems effects. As stated earlier, we are not offering a formal model in which these features represent particular values for choice variables and parameters that together constitute the arguments of a supermodular objective function or of the payoff functions in a supermodular game. Still, when we argue that two features are complementary, we will mean precisely that doing (more of) one increases the returns to doing (more of) the other. One way to evaluate complementarities in the Japanese economy involves conceiving of it a 7. Parts of this analysis first appeared in Milgrom and Roberts (1992). For richer descriptions of the characteristic features of Japanese organization, see Aoki (1988) and Ito (1991).

10 supermodular game, where the players are individual consumers, workers and firms. In this case, some of the complementarities are strategic: One player's undertaking some activity increases the returns to some activity (perhaps the same one) for other players. Nevertheless, we will for the most part attempt to interpret the good past performance of the Japanese economy as emerging from coherent practices in an environment rife with complementarities. That simplifies our exposition by allowing us to avoid issues of how the diverse decision makers are led to pursue coherent policies and focuses instead on why the policies are coherent. Thus, we will usually describe complementarities as if the economy shared a single objective of producing value, with occasional remarks where the concept of strategic complementarity would apply under the game interpretation. Much of our discussion focuses on practices of the largest firms in Japan. These companies are not generally representative of all of Japanese business. Indeed, the practices of small and medium-sized firms that are responsible for the bulk of Japanese GNP are quite different in many regards. Nevertheless, the large firms play a special, central role in Japanese economy and in Japanese life. Two policies have been most frequently noted in discussions of the human resource practices in major Japanese firms: long-term employment guarantees for so-called permanent employees,8 and recruiting of permanent employees only at the very early stages of their careers. These two features are not uniquely Japanese, nor are they followed universally by all major Japanese firms. Nor are they particularly common in small and medium-sized businesses in Japan. They do, however, appear to be carried further in major Japanese firms than elsewhere. At least since the early 1950s, it has been extremely rare for a major Japanese firm to dismiss a permanent employee except for specific cause, let alone to institute a mass layoff. This has been true both for white-collar and blue-collar workers, and both groups have long expected to enjoy employment security unless their employer was faced by imminent failure. Even when major firms have closed, they have often found their employees other jobs with related firms (see Sheard (1992)). As we will discuss below, the employment guarantee has not been open-ended ─ it does not extend through to normal retirement age, and so the frequently used terminology of “life-time employment” is inappropriate in this regard ─ but it has been real. It has been similarly rare for a major firm to hire someone at other than one of the lowest entry levels. These firms recruit directly from high school and the top universities, and all the new employees of a given year's cohort start work together on April first of that year. There is some mobility of employees in the first year or so, when obvious mismatches are corrected, but after that there is little or no hiring from outside. One effect of these policies has been to reduce turnover among permanent employees of 8. Some large Japanese firms have made use of workers to whom no long-term employment promise was made. In many cases, however, these “contract workers” have been kept on by the firms in question for long periods. Married women whose children were in school and who had returned to the workplace have often been employed on this basis. (Until quite recently, younger women who joined large firms after high school or university were expected to leave at an early age to marry and raise children, and little provision was made for their continuing employment.)

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1 be a thing of the past. A variety of developments in Japanese society and politics and in the position of the Japanese economy in the world have worsened the fit between the current system and its environment and are threatening the continued viability of some of the key elements of the current system. If our arguments are correct, so that the Japanese system is one in which the individual elements are linked by complementarity and form a coherent pattern, then these developments that necessitate changes in a few of the features of the current organizational arrangements may ultimately lead to widespread, systemic changes. In a system of complements, altering the values of a few of the variables leads to predictable changes in the other variables. In the Japanese context, these effects will amount to a fundamental realignment of the patterns of economic organization. An appreciation of the need for economic change, and even for the possibility that the changes may end up being be fundamental and systemic, seems to be developing in Japan. Even before it became clear how severe and extended the current recession would prove to be, discussion had begun about the continued appropriateness or viability of some of the characteristic features of Japanese economic organization in light of secular trends and developments. For example, in 1993 Akio Morita, Chairman of the Sony Corporation, called for Japanese business to adopt shorter working hours, higher pay, higher dividends, and a greater orientation towards profit rather than market share. These changes were seen as moves towards doing business as it is done elsewhere in the world. They were justified not as necessarily being desirable on their own, but instead as being needed if Japan is to be a “good world citizen” whose policies and practices were compatible with those of its major trading partners. Morita's suggestions apparently did not meet with any wide acceptance, but others have echoed similar concerns with the fit between Japan and other economies. Other business leaders, notably Ken-Ichi Ohmae of McKinsey & Company, have pushed for re-orienting Japanese politics and policy on purely domestic grounds. The organization founded and led by Ohmae, Reform of Heisei, has attracted immense popular attention with its call for reforms that would favor consumer interests and those of “outsider” firms (new businesses and foreign firms) that are more likely to cater to consumer needs, over those of established big business. The stunning defeat of the Liberal Democratic Party, which had completely dominated post-War Japanese politics, in the 1993 election and the formation of the Hosakawa government with its promise of electoral and administrative reform and of economic deregulation signaled both the Japanese electorate's disgust with the prevailing system and their desires for political and economic change. The recession that began in 1991 in Japan and that has extended into 1994 is intensifying concern with the need for economic change. The forces that have created these needs are, however, of longer standing. We have argued that capital market conditions and practices have been key elements in the Japanese model. These are all changing in ways that threaten existing organizational patterns. Regulatory changes have already given rise to vested pension plans and to increased competition to invest and manage these. If U.S. experience is any guide, this may force the pension fund managers to insist on greater profits and payouts from the firms whose stocks they hold, endangering the policies of retaining the large bulk of corporate earnings and of accentuating growth and market share. More generally, on-going deregulation of the Japanese financial institutions is opening world capital markets to Japanese savers and so raising their required returns to world levels. This too will

2 lead to pressure for corporations to generate higher returns for investors. Meanwhile, Japanese firms (and especially the largest ones and those belonging to horizontal keiretsu) have earned returns that matched their low perceived costs of capital and that resulted from their growth-oriented policies, but that were well below those generated by corporations elsewhere. These changes have been going on for some time, but initially the pressures for better performance were muted by the huge capital gains that resulted from the spectacular run-up of stock and land prices in the “Bubble Economy” of the late 1980s. This boom was occasioned by the Bank of Japan's keeping interest rates extremely low in the face of the huge rise in the value of the yen that followed the Plaza Accord. Investor beliefs that these gains would continue to mount also kept the perceived cost of capital low, because firms were able to issue corporate debt at negligible interest rates by offering warrants. For example, Sony financed some of its 1989 acquisition of Columbia Pictures, the Hollywood movie studio, with bonds carrying warrants. The interest rate on the bonds was less than a third of one percent! The collapse of stock and real estate prices at the end of the Bubble Economy, however, not only removes the safety valve of capital gains, but is likely to intensify the pressure for improved financial performance. The decreased asset values have also made it more difficult for the banks to finance expansive policies, especially because their portfolios contain large amounts of effectively non-performing loans. Stock market prices being at half their peak values further contributes to an increased cost of capital and further erodes the attractiveness of deferring profits to buy growth in market share. The rise in the cost of capital is unlikely to reverse itself. In particular, the Japanese population is aging rapidly, and in 1996 14% percent of the population will be over age 65. This represents a doubling in only 26 years, and the aging will continue. (In contrast, it took 75 years in the U.S. for the percentage of the population over 65 to double from 7% to 14%, 45 years in the United Kingdom and 115 years in France!) Meanwhile, the size of the labor force is projected to peak in the year 2000, and then to begin to fall. These demographic developments will reduce future domestic savings rates and are likely to put further pressure on the cost of capital, making growth and market share policies more difficult to maintain. This in turn threatens all the other features to which they are linked. The gradual opening of Japanese product and service markets is also threatening established practices. While blue-collar, manufacturing productivity in many Japanese industries is among the highest in the world, white collar productivity is low by international standards, especially in services (McKinsey Global Institute, 1992, 1993). The extreme manifestations of this are the “window sitters,” employees who have no work but are simply assigned to sit at their desks by the window until they retire. The productivity problems are in part a result of the permanent employment policies and the use of promotions as rewards. The former has made shedding unproductive workers difficult, and the latter has resulted in excessive numbers of employees at high levels. Consensus decision making may have contributed as well: Honda recently shifted away from this approach, even though it was one of the cherished values of the firm, because its executives believed it rendered decision making too slow and unresponsive. The intense hiring by large firms during the Bubble Economy, when capital seemed free and when anticipated future labor shortages seemed a pressing concern, and the current recession have intensified the effects of these long-term

3 trends. As long as Japanese markets were relatively closed, these inefficiencies could be financed by high domestic prices. Markets are gradually opening, however, under the effects of deregulation, the reduction of non-tariff trade barriers, and a breakdown in norms against price competition. Competition, both from foreign products and firms and from new Japanese entrants, is intensifying and, increasingly, shifting towards price competition. For example, the U.S. personal computer maker Compaq recently entered the Japanese market at prices that were half what the major Japanese firms had been charging for similar equipment, while a new direct-importer of Scotch whisky has so undercut the previously established prices that duty-free imports of Scotch by Japanese travelers have fallen 80 percent. These developments are putting pressure to lower overhead costs. These in turn endanger the permanent employment policy. Finally, the growth of the Japanese economy is sure to be much less in the future than it has been in the past. The Japanese population is forecast to stop growing and actually to start shrinking by 2010, with an increasingly large percentage of the population having retired from the work force. Thus, growth in the labor supply will not contribute to overall economic growth. Capital deepening is a possible means of growth, but the rising costs of capital will limit this, and, at least for the present, Japanese industry faces massive over-capacity already. Moreover, Japanese firms are now operating on the technological frontier and cannot expect to continue to be significant net importers of superior technology, as they once were. All this makes it very difficult for the Japanese economy to grow at rates that much exceed those of the other advanced economies. All these factors make the strategy of running the firm in the interests of long-term growth and continuing employment more difficult to maintain. At the same time, Japanese employees are increasingly willing to change jobs in mid-career. This trend seems to have started among managerial employees who had studied abroad and who were frustrated by the slow pace of advancement in their firms. They were then recruited by foreign firms seeking Japanese managers. It has, however, begun to spread beyond the foreign-trained and foreign firms. The long-term labor shortages that are predicted to follow from the established demographic trends of low birth rates and minimal immigration should intensify this trend, as should many of the changes in attitudes among younger generations towards work and employers that surveys have revealed. Increasingly, younger Japanese appear to be unwilling to devote themselves to work and to identify their interests with those of their employers to the extent that their parents did. Again, if the linkages among aspects of Japanese practice are as we have suggested, a breakdown in the permanence of employment will require many other fundamental changes. While these secular developments are going on, the continuing recession has put special pressures on Japanese businesses. Under the pressure of the recession, with falling sales and profits, firms are actively considering ways to increase white-collar productivity, for example, by increasing the sensitivity of managerial pay to individual performance. Doing so, however, risks undercutting the other aspects to which pay policies are linked. Many have even begun to question openly the continued viability of permanent employment, and others simply state that it is a thing of the past. Already a number of firms have not renewed contract workers' employment, and some have actually terminated regular employees (usually via pressured early retirements, but increasingly through direct layoffs). Even if the permanent employment policy is not officially abandoned, these forced quits will undermine its credibility.

With so many of the characteristic features of Japanese economic organization being challenged, it is clear that major changes will be needed in the economy. Combined with the multiplier effect that theory tells us is always associated with systems of complements, we are led to expect that the changes will have to be even larger and more pervasive than might otherwise appear. Perhaps the most interesting question is what new pattern will ultimately emerge. In particular, many Japanese are concerned with whether their economy must necessarily end up in the American mold. Our analysis might suggest this, because parts of the analysis were written as if the Japanese and U.S. approaches were the fundamental alternatives. But that was merely a convenient assumption. Identifying the actual range of alternatives is beyond the scope of our analysis or the range of our forecasting powers.

NAMs出版プロジェクト: ミルグロム『組織の経済学』1997 契約理論

http://nam-students.blogspot.jp/2016/10/blog-post_10.html

上記vii日本語版序文で言及された続編

Complementarities and systems: Understanding japanese economic organization

Paul Milgrom (milgrom@stanford.edu) and John Roberts
Estudios Económicos, 1994, vol. 9, issue 1, 3-42

https://pdfs.semanticscholar.org/bfad/82abf071da886193bf990b9562f1010a5bd5.pdf

バージョン違いがあるらしい

青木昌彦が参照される
https://ja.wikipedia.org/wiki/%E9%9D%92%E6%9C%A8%E6%98%8C%E5%BD%A6
Information, Incentives, and Bargaining in the Japanese Economy, Cambridge University Press, (1988年)
　=永易浩一訳『日本経済の制度分析―情報・インセンティブ・交渉ゲーム』筑摩書房、1992年
The Japanese Firm: the Sources of Competitive Strength, with Ronald Dore, (Oxford University Press, 1994).
　=NTTデータ通信システム科学研究所訳『国際・学際研究システムとしての日本企業』（NTT出版、1995年）
他

青木昌彦「福島原発事故に学ぶ — 危機に強い産業組織築け」2011年8月4日
http://nam-students.blogspot.jp/2016/03/201184.html

ただし青木はTPP推進派

日本の補完性ネットワークの強さが検証される