Principal Contributions: My contributions to economics and other social sciences cover six areas.
(1) Disequilibrium Dynamics.
I have integrated Knut Wicksell's theory of cumulative process and J. M. Keynes' theory of effective demand. Having constructed a model of monopolistically competitive firms as a micro-foundation for the decentralized price mechanism, I have demonstrated that, if, in a monetary economy, prices and wages are flexible, a deviation from equilibrium inevitably produces errors in firms' expectations and starts a dynamic process that drives prices and wages cumulatively away from equilibrium. I have then argued, in opposition to the neoclassical view of the self-regulating nature of laissez-faire markets, that what stabilizes the monetary economy is the inflexibility of prices and wages and that an equilibrium it gravitates to almost never achieves full-employment. I have also proved that, so long as prices and wages have downward inflexibility, the trade-off between unemployment and inflation never ceases to exist no matter how long the time span.
(2) Evolutionary Models.
I have developed mathematical models of Schumpeterian evolutionary processes that describe how a large number of firms interact with one another, by competing to innovate, trying to imitate and struggling to grow. Over a long span of time, I have argued, what the economy approaches is not a neoclassical equilibrium of uniform technology, but at best a statistical equilibrium of technological disequilibria. Profits in excess of normal rate, therefore, never vanish from the economy.
(3) Bootstrap Theory of Money.
I have formulated a search-theoretic model of the decentralized exchange economy that is capable of characterizing a barter system, a commodity-money system, a token-money system, and a gift-exchange system as four different forms of its exchange equilibria. I was able to show that while the barter system requires a double coincidence of wants between traders and the gift-exchange system requires an infinite memory of all the past transactions, the monetary system, whether it uses a commodity-money or a token-money, is a "bootstrap" equilibrium that needs neither "real" conditions nor "informational" requirement to support itself as an equilibrium. (The monetary system does not even need any "fiat" by the government to sustain itself.) Everybody accepts money as money simply because everybody expects everybody else will accept it as money. It is because of such "pure bootstrap" nature, I have then argued, money can be regarded, together with language and law, as an entity of the third type – a "social entity" – distinct from physical and biological entities.
(4) Theory of Corporation.
In opposition to the mainstream economic theory that views both firms and corporations as mere nexuses of contractual relations, I have presented a new characterization of the business corporation as a for-profit firm that consists of two-tier ownership relations: the corporation as a legal person owns corporate assets and the corporation is in turn owned by shareholders as a thing (i.e., as a bundle of rights). My contention is that it is this person/thing duality of the corporation that is responsible for the age-old controversy over the "essence" of corporate personality as well as the wide variations of corporate structures we observe among today's advanced capitalist economies. Such characterization has enabled me to reject the widely-held view of corporate managers as agents of shareholders and to revive the old system of corporate governance that places corporate managers' fiduciary duties to the corporation at its foundation.
(5) Theory of Fiduciary Relationships.
In recent years, I have been working on unifying the theory of fiduciary relationships. Starting from the fundamental legal axiom that one may not contract with oneself, I have characterized fiduciary law as a law that imposes a duty of loyalty as a legally enforceable duty on a person forming a relationship with another that would degenerate into a contract with oneself were that relationship contractually sustained. I have also shown how the fiduciary law solves this apparent muddling of ethics and law by placing the burden of proof on accused fiduciaries and relying on their unauthorized gains as verifiable lower-bound measures of beneficiaries' lost expectations.
(6) Optimal Growth Theory.
I have worked out an optimal growth model for the non-additive intertemporal utility function. It is regarded as one of the first contributions to the field of complex economic dynamics.
Concurrently with these academic works, I have also written books and essays (mostly in Japanese) on global capitalism, post-modernity, civil society, the future of corporate systems, cryptocurrencies, money and language, Shakespeare, and Ihara Saikaku.