Philippe Aghion

A Theory of Trickle-Down Growth and Development

This paper develops a model of growth and income inequalities in the presence of imperfect capital markets, and it analyses the trickle-down effect of capital accumulation. Moral hazard with limited wealth constraints on the part of the borrowers is the source of both capital market imperfections and the emergence of persistent income inequalities. Three main conclusions are obtained from this model. First, when the rate of capital accumulation is sufficiently high, the economy converges to a unique invariant wealth distribution. Second, even though the trickle-down mechanism can lead to a unique steady-state distribution under laissez-faire, there is room for government intervention: in particular, redistribution of wealth from rich lenders to poor and middle-class borrowers improves the production efficiency of the economy both because it brings about greater equality of opportunity and also because it accelerates the trickle-down process. Third, the process of capital accumulation initially has the effect of widening inequalities but in later stages it reduces them: in other words, this model can generate a Kuznets curve.

Growth and Unemployment

This paper analyses the effects of growth on long-run unemployment using a search model of equilibrium unemployment where growth arises explicitly from the introduction of new technologies that require labour reallocation for their implementation. The analysis uncovers and compares between two competing effects of growth on unemployment. The first is a capitalisation effect, whereby an increase in growth raises the capitalised returns from creating jobs and consequently reduces the equilibrium rate of unemployment. The second is a creative destruction effect whereby an increase in growth reduces the duration of a job match, thereby raising the equilibrium level of unemployment both directly, by raising the job separation rate, and indirectly, by discouraging the creation of job vacancies.

Currency Crises and Monetary Policy in an Economy with Credit Constraints

This paper presents a simple model of currency crises which is driven by the interplay between the credit constraints of private domestic firms and the existence of nominal price rigidities. The possibility of multiple equilibria, including a ‘currency crisis’ equilibrium with low output and a depreciated domestic currency, results from the following mechanism: If nominal prices are ‘sticky’, a currency depreciation leads to an increase in the foreign currency debt repayment obligations of firms, and thus to a fall in their profits; this reduces firms’ borrowing capacity and therefore investment and output in a credit-constrained economy, which in turn reduces the demand for the domestic currency and leads to a depreciation. We examine the impact of various shocks, including productivity, fiscal, or expectational shocks. We then analyze the optimal monetary policy to prevent or solve currency crises. We also argue that currency crises can occur both under fixed and flexible exchange rate regimes as the primary source of crises is the deteriorating balance sheet of private firms.

Innovation and Institutional Ownership

We find that institutional ownership in publicly traded companies is associated with more innovation (measured by cite-weighted patents). To explore the mechanism through which this link arises, we build a model that nests the lazy-manager hypothesis with career-concerns, where institutional owners increase managerial incentives to innovate by reducing the career risk of risky projects. The data supports the career concerns model. First, whereas the lazy manager hypothesis predicts a substitution effect between institutional ownership and product market competition (and managerial entrenchment generally), the career-concern model allows for complementarity. Empirically, we reject substitution effects. Second, CEOs are less likely to be fired in the face of profit downturns when institutional ownership is higher. Finally, using instrumental variables, policy changes and disaggregating by type of owner we find that the effect of institutions on innovation does not appear to be due to endogenous selection.

On the Speed of Transition in Central Europe

Transition in Central Europe is four years old. State firms which dominated the economy are struggling with market forces. A new private sector quickly emerged and has taken hold. Unemployment, which did not exist, is high and still increasing. Will this process of transition accelerate, or slow down? Will unemployment keep increasing? Can things go wrong and how? Our paper represents a first pass at answering those questions. The basic structure of the model we develop is standard, that of the transition from a low to a high productivity sector. But we pay attention to two aspects which strike us as important. The first is the interactions between unemployment and the decisions of both state and private firms. The second are the idiosyncracies which come from the central planning legacy, from the structure of control within state firms to the lack of many market institutions, which limits private sector growth. We start with a description of transition in Poland so far. We then develop a model and use it to think about the determinants of the speed of transition and the level of unemployment. Finally, we return to the role of policy and the future in Poland, as well as the causes of cross-Central European country variations.

Technology, Information, and the Decentralization of the Firm

This paper develops a framework to analyze the relationship between the diffusion of new technologies and the decentralization decisions of firms. Centralized control relies on the information of the principal, which we equate with publicly available information. Decentralized control, on the other hand, delegates authority to a manager with superior information. However, the manager can use her informational advantage to make choices that are not in the best interest of the principal. As the available public information about the specific technology increases, the trade-off shifts in favour of centralization. We show that firms closer to the technological frontier, firms in more heterogeneous environments and younger firms are more likely to choose decentralization. Using three datasets of French and British firms in the 1990s, we report robust correlations consistent with these predictions.

Dualism and Macroeconomic Volatility

This paper develops a simple macroeconomic model that shows that combining capital market imperfections together with unequal access to investment opportunities across individuals can generate endogenous and permanent fluctuations in aggregate GDP, investment, and interest rates. Reducing inequality of access may be a necessary condition for macroeconomic stabilization. Moreover, countercyclical fiscal policies have a role to play: in our model savings are underutilized in slumps because of the limited debt capacity of potential investors. Therefore, the government should issue public debt during recessions in order to absorb those idle savings and finance investment subsidies or tax cuts for investors.

Competition and growth with step-by-step innovation: An example

This paper develops a simple example to analyse the relationship between product market competition and growth in a model with step-by-step innovations, where laggards can never leapfrog the current industry leaders, but instead must first catch up with the leaders before battling for technological leadership in the future. Unlike in existing Schumpeterian models of growth, more intense product market competition and/or imitations may be growth-enhancing.

Volatility and Growth: Credit Constraints and Productivity-Enhancing Investment

We examine how credit constraints affect the cyclical behavior of productivity-enhancing investment and thereby volatility and growth. We first develop a simple growth model where firms engage in two types of investment: a short-term one and a long-term productivity-enhancing one. Because it takes longer to complete, long-term investment has a relatively less procyclical return but also a higher liquidity risk. Under complete financial markets, long-term investment is countercyclical, thus mitigating volatility. But when firms face tight credit constraints, long-term investment turns procyclical, thus amplifying volatility. Tighter credit therefore leads to both higher aggregate volatility and lower mean growth for a given total investment rate. We next confront the model with a panel of countries over the period 1960-2000 and find that a lower degree of financial development predicts a higher sensitivity of both the composition of investment and mean growth to exogenous shocks, as well as a stronger negative effect of volatility on growth.

Optimal learning by experimentation

This paper considers a problem of optimal learning by experimentation by a single decision maker. Most of the analysis is concerned with the characterisation of limit beliefs and actions. We take a two-stage approach to this problem: first, understand the case where the agents payoff function is deterministic; then, address the additional issues arising when noise is present. Our analysis indicates that local properties of the payoff function (such as smoothness) are crucial in determining whether the agent eventually attains the true maximum payoff or not. The paper also makes a limited attempt at characterising optimal experimentation strategies.