In the area of dynamic economics, David Cass’s work has spawned a number of important lines of research, including the study of dynamic general equilibrium theory, the concept of sunspot equilibria, and general equilibrium theory when markets are incomplete. Based on these contributions, this volume contains new developments in the field, written by Cass's students and co-authors.

This book, as the title suggests, explains how General equilibrium, the dominant conceptual framework in mainstream economics, describes a perfectly impossible world. Even with its counterfactual assumptions taken for granted, it fails on many levels. Under the impressive editorship of Ackerman and Nadal, this book will appeal to students and researchers in economics and related social science disciplines.

This thesis consists of three chapters studying dynamic economies in general equilibrium. The first chapter considers an economy in business cycles with potentially imperfect financial markets. The second chapter investigates an economy in its balanced growth path with heterogeneous firms. The third chapter analyzes dynamic competitions that these firms are potentially engaged in. The first chapter, "Asset Price and Real Investment Volatility with Heterogeneous Beliefs," sheds light on the role of imperfect financial markets on the economic and financial crisis 2007-2008. This crisis highlights the role of financial markets in allowing economic agents, including prominent banks, to speculate on the future returns of different financial assets, such as mortgage-backed securities. I introduce a dynamic general equilibrium model with aggregate shocks, potentially incomplete markets and heterogeneous agents to investigate this role of financial markets. In addition to their risk aversion and endowments, agents differ in their beliefs about the future aggregate states of the economy. The difference in beliefs induces them to take large bets under frictionless complete financial markets, which enable agents to leverage their future wealth. Consequently, as hypothesized by Friedman (1953), under complete markets, agents with incorrect beliefs will eventually be driven out of the markets. In this case, they also have no influence on asset prices and real investment in the long run. In contrast, I show that under incomplete markets generated by collateral constraints, agents with heterogeneous (potentially incorrect) beliefs survive in the long run and their speculative activities drive up asset price volatility and real investment volatility permanently. I also show that collateral constraints are always binding even if the supply of collateralizable assets endogenously responds to their price. I use this framework to study the effects of different types of regulations and the distribution of endowments on leverage, asset price volatility and investment. Lastly, the analytical tools developed in this framework enable me to prove the existence of the recursive equilibrium in Krusell and Smith (1998) with a finite number of types. This has been an open question in the literature. The second chapter, "Innovation from Incumbents and Entrants," is a joint work with Daron Acemoglu. We propose a simple modification of the basic Schumpeterian endogenous growth models, by allowing incumbents to undertake innovations to improve their products. This model provides a tractable framework for a simultaneous analysis of entry of new firms and the expansion of existing firms, as well as the decomposition of productivity growth between continuing establishments and new entrants. One lesson we learn from this analysis is that, unlike in the basic Schumpeterian models, taxes or entry barriers on potential entrants might increase economic growth. It is the outcome of the greater productivity improvements by incumbents in response to reduced entry, which outweighs the negative effect of the reduction in creative destruction. As the model features entry of new firms and expansion and exit of existing firms, it also generates an equilibrium firm size distribution. We show that the stationary firm size distribution is Pareto with an exponent approximately equal to one (the so-called "Zipf distribution"). The third chapter, "Racing: when should we handicap the advantaged competitor?" studies dynamic competitions, for example R & D competitions used in the second chapters. Two competitors with different abilities engage in a winner-take-all race; should we handicap the advantaged competitor in order to reduce the expected completion time of the race? I show that if the discouragement effect is strong, i.e., both competitors are discouraged from exerting effort when it becomes more certain who will win the race, we should handicap the advantaged. We can handicap him either by reducing his ability or by offering him a lower reward if he wins. Doing so induces higher effort not only from the disadvantaged competitor because of his higher incentive from a higher chance of winning the race but also from the advantaged competitor because of their strategic interactions. Therefore, the expected completion time is strictly shortened. To prove the existence and uniqueness of the equilibria (including symmetric and asymmetric equilibria) that leads to the conclusion, I use a boundary value problem formulation which is novel to the dynamic competition literature. In some cases, I obtain closed-form solutions of the equilibria.

This PhD thesis aims to look at four major issues in political economy and macroeconomics, namely, tax evasion, spirit of capitalism, globalisation and production structures involving delayed effects of inputs in dynamic general equilibrium models. These issues are of importance to any economy, but more so to an emerging economy like South Africa. The thesis will not only aim to obtain optimal policy responses in the presence of such distortions (deviations from the traditional Neoclassical world), but will also analyse the effects of these distortions on the growth and welfare of the economy. The thesis aims to have four separate papers based on dynamic general equilibrium (DGE) models: The first paper would aim to explain theoretically why tax evasion might depend on the level of financial development and the inflation rate in the economy. And then, it would try and test whether our proposed theoretical linkage holds in the data using panel data of 150 countries covering the period of 1980-2009. General equilibrium models that include the spirit of capitalism shows a positive relationship between growth and inflation aÌ22́Ơ0́− something unobserved in the data. The literature has tried to reconcile this theoretical and empirical mismatch by introducing human capital, cash-in-advance constraints applying to only specific kind of (non-productive) goods, etc. In the second paper, we, however, aim to show that a simpler way of achieving the negative inflationaÌ22́Ơ0́−growth relationship would be to introduce a banking system in the model subjected to cash reserve requirements. The third paper examines the effect of openness on economic growth, given a human capital accumulation function that captures the marginal benefit of knowledge spillovers in an economy. Two opposing effects are highlighted aÌ22́Ơ0́− one a positive effect from the increase in human capital on growth, the other a negative effect through an increase in seigniorage taxes aÌ22́Ơ0́− that would suggest there is a threshold value of openness, beyond which the impact of opening the economy even more becomes negative for economic growth. The fourth paper would aim to indicate that in the presence of lagged inputs, and especially lagged capital input, in the production structure of an economy, an inflation targeting country might experience aÌ22́Ơ¿3chaoticaÌ22́Ơ℗+ growth behaviour if the inflation target is set too high.

This book addresses major issues such as a growing world energy demand, environmental degradation due to anthropogenic greenhouse gas (GHG) emission, and risk management of disastrous events such as pandemics, abnormal climate, and earthquakes. Using cutting-edge analytical tools, particularly computable general equilibrium (CGE) modelling, the analyses are focused on a very wide range of policy-relevant economic questions for the Asia-Pacific region, especially for Japan, China, India, Vietnam, and smaller nations, including Brunei, Timor Leste, and Fiji. The first part considers (a) the effects of climate change on agriculture sectors, energy policies, and future GHG emission trends, (b) adaptation to climate changes in energy policy and its impacts on the economies, and (c) risk management of catastrophic events such as global pandemics. The second part examines (a) energy environmental issues, (b) economic impacts of natural disaster and depopulation, and (c) effects of informatics development on risk management, using CGE modelling and other methods in regional science fields. Contributors are internationally active leading CGE modellers and environmental economists. The book should be greatly beneficial for scholars and graduate students as well as policy makers who are interested in the economic effects and management of risks relating to climate change and disastrous events.