荷姆斯壯在1970年代末期提出的「資訊內含原則」，解釋委任人（例如公司股東）應該替經理人（例如公司執行長）設計最佳契約，將經理人的薪資與績效相關的資訊建立連結。根據其理論，最佳契約就是能提供經理人足夠的誘因為委任人賣力，但又不至於讓委任人的利益陷入風險。荷姆斯壯的理論主張，公司股東必須替經理人設計最佳契約。若契約有缺失，經理人可能在短期內創造現金流，製造漂亮財報，藉此獲得更高紅利，但卻忽略公司長期的健全性。此作法到後期，恐會掏空公司資產，經理人賺飽後走人。
哈特則在1980年代中期提出「不完整契約」，替契約理論另闢新徑。他主張不可能在一份合約中顧及所有層面，所以必須善加分配控制權。他的理論對企業的所有權及控制提供新思維，廣泛應用在經濟、政治和法律層面，例如：公司合併、債務和股本的適當比例，或學校、監獄該私有化或公營的問題。
Congratulations to Professor Oliver Hart, a former undergraduate at King’s College (1966), and a former Fellow of Churchill College, who has been jointly awarded the 2016 Economics Nobel Prize this morning.
Press Release: The Prize in Economic Sciences 2016
10 October 2016
The Royal Swedish Academy of Sciences has decided to award the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2016 to
Oliver Hart
Harvard University, Cambridge, MA, USA
Harvard University, Cambridge, MA, USA
and
Bengt Holmström
Massachusetts Institute of Technology, Cambridge, MA, USA
Massachusetts Institute of Technology, Cambridge, MA, USA
“for their contributions to contract theory”
The long and the short of contracts
Modern economies are held together by innumerable contracts. The new theoretical tools created by Hart and Holmström are valuable to the understanding of real-life contracts and institutions, as well as potential pitfalls in contract design.
Society’s many contractual relationships include those between shareholders and top executive management, an insurance company and car owners, or a public authority and its suppliers. As such relationships typically entail conflicts of interest, contracts must be properly designed to ensure that the parties take mutually beneficial decisions. This year’s laureates have developed contract theory, a comprehensive framework for analysing many diverse issues in contractual design, like performance-based pay for top executives, deductibles and co-pays in insurance, and the privatisation of public-sector activities.
In the late 1970s, Bengt Holmström demonstrated how a principal (e.g., a company’s shareholders) should design an optimal contract for an agent (the company’s CEO), whose action is partly unobserved by the principal. Holmström’s informativeness principle stated precisely how this contract should link the agent’s pay to performance-relevant information. Using the basic principal-agent model, he showed how the optimal contract carefully weighs risks against incentives. In later work, Holmström generalised these results to more realistic settings, namely: when employees are not only rewarded with pay, but also with potential promotion; when agents expend effort on many tasks, while principals observe only some dimensions of performance; and when individual members of a team can free-ride on the efforts of others.
In the mid-1980s, Oliver Hart made fundamental contri-butions to a new branch of contract theory that deals with the important case of incomplete contracts. Because it is impossible for a contract to specify every eventuality, this branch of the theory spells out optimal allocations of control rights: which party to the contract should be entitled to make decisions in which circumstances? Hart’s findings on incomplete contracts have shed new light on the ownership and control of businesses and have had a vast impact on several fields of economics, as well as political science and law. His research provides us with new theoretical tools for studying questions such as which kinds of companies should merge, the proper mix of debt and equity financing, and when institutions such as schools or prisons ought to be privately or publicly owned.
Through their initial contributions, Hart and Holmström launched contract theory as a fertile field of basic research. Over the last few decades, they have also explored many of its applications. Their analysis of optimal contractual arrangements lays an intellectual foundation for designing policies and institutions in many areas, from bankruptcy legislation to political constitutions.
Read more about this year's prize
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Illustration: © Johan Jarnestad/The Royal Swedish Academy of Sciences
Oliver Hart, born 1948 in London, UK. Ph.D. 1974 from Princeton University, NJ, USA. Andrew E. Furer Professor of Economics at Harvard University, Cambridge, MA, USA.
http://scholar.harvard.edu/hart/home
http://scholar.harvard.edu/hart/home
Bengt Holmström, born 1949 in Helsinki, Finland. Ph.D. 1978 from Stanford University, CA, USA. Paul A. Samuelson Professor of Economics, and Professor of Economics and Management at Massachusetts Institute of Technology, Cambridge, MA, USA.
http://economics.mit.edu/faculty/bengt
http://economics.mit.edu/faculty/bengt
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