Yongsung Chang

Learning-by-Doing as a Propagation Mechanism

This Paper suggests that skill accumulation through past work experience, or ‘learning-by-doing’ (LBD), can provide an important propagation mechanism in a dynamic stochastic general equilibrium model, as the current labour supply affects future productivity. Our econometric analysis uses a Bayesian approach to combine micro-level panel data with aggregate time series. Formal model evaluation shows that the introduction of the LBD mechanism improves the models ability to fit the dynamics of aggregate output and hours.

Do Technological Improvements in the Manufacturing Sector Raise or Lower Employment

We find that technologys effect on employment varies greatly across manufacturing industries. Some industries exhibit a temporary reduction in employment in response to a permanent increase in TFP, whereas far more industries exhibit an employment increase in response to a permanent TFP shock. This raises serious questions about existing work that finds that a labor productivity shock has a strong negative effect on employment. There are tantalizing and interesting differences between TFP and labor productivity. We argue that TFP is a more natural measure of technology because labor productivity reflects shifts in the input mix as well as in technology.

Understanding How Price Responds to Costs and Production

The importance of sticky prices in business cycle fluctuations has been debated for many years. But we argue, based on a large empirical literature from the 1950s and 60s, that it is necessary to distinguish the response of price to an increase in factor prices from its response to an increase in marginal cost generated by an expansion in production. Consistent with that earlier literature, we find for 450 U.S. manufacturing industries that prices do respond more to increases in costs driven by changes in factor prices than to increases in marginal cost precipitated by expansions in output. We explore two models that can potentially explain these findings. Both break the link between price and marginal cost, thereby generating what one might naively interpret as average-cost pricing. The first is driven by firms pricing to limit entry. The second is driven by firms pricing to limit non-price competition within their market.

Wages, business cycles, and comparative advantage

The standard equilibrium models of business cycles face a puzzling fact that total hours vary greatly over the business cycle without much variation in aggregate wages. The model augments the standard RBC model to include Lucas span of control. Distinction between market and non-market and managerial and non-managerial work makes aggregate wages far less cyclical than individual wages. Cross-sectional comparative advantage between market and non-market sector in the workforce substantially increases the response of aggregate hours to shifts in relative productivity. As a result, the model provides a reconciliation between data and equilibrium macroeconomics.

Heterogeneity and Aggregation in the Labor Market: Implications for Aggregate Preference Shifts

The cyclical behavior of hours of work, wages, and consumption does not conform with the prediction of the representative agent with standard preferences. The residual in the intra-temporal first-order condition for commodity consumption and leisure is often viewed as a failure of labor-market clearing. We show that a simple heterogeneous agent economy with incomplete markets and indivisible labor generates an aggregation error that looks much like the preference residual in aggregate data. Our results caution against viewing the preference residual as a failure of labor-market clearing or a fundamental driving force of business cycles.

How Sticky Wages In Existing Jobs Can Aect Hiring

We consider a matching model of employment with wages that are flexible for new hires, but sticky within matches. We depart from standard treatments of sticky wages by allowing effort to respond to the wage being too high or low. Shimer (2004) and others have illustrated that employment in the Mortensen-Pissarides model does not depend on the degree of wage flexibility in existing matches. But this is not true in our model. If wages of matched workers are stuck too high in a recession, then firms will require more effort, lowering the value of additional labor and reducing new hiring.

Welfare costs of sticky wages when effort can respond

We examine the impact of wage stickiness when employment has an effort as well as hours dimension. Despite wages being predetermined, the labor market clears through the effort margin. Consequently, welfare costs of wage stickiness are potentially much, much smaller.

Transition Dynamics in the Neoclassical Growth Model: The Case of South Korea

Many cases of successful economic development, such as South Korea, exhibit long periods of sustained capital accumulation rates. This empirical feature is at odds with the standard neoclassical growth model which predicts initially high and then declining capital accumulation rates. We show that minor modifications of the neoclassical model go a long way towards accounting for the transition dynamics of the South Korean economy. Our modifications recognize that (1) agriculture essentially does not use reproducible capital, and that during the transition period (2) the relative price of capital declines substantially, and (3) the nonfarm employment share increases substantially.

Understanding How Employment Responds to Productivity Shocks in a Model with Inventories

Whether technological progress raises or lowers aggregate employment in the short run has been the subject of much debate in recent years. Using a simple model of industry employment, we show that cross-industry differences of inventory holding costs, demand elasticities, and price rigidities potentially all affect employment decisions in the face of productivity shocks. In particular, the employment response to a permanent productivity shock is more likely to be positive the less costly it is to hold inventories, the more elastic industry demand is, and the more flexible prices are. Using data on 458 4-digit U.S. manufacturing industries over the period 1958-1996, we find statistically significant effects of variations in inventory holdings and demand elasticities on short-run employment responses, but find less evidence pertaining to the effects of measured price stickiness.

Decomposition of hours based on extensive and intensive margins of labor

Abstract We decompose the underlying disturbances in total hours into three kinds: disturbances that shift the level of employment in the long run, those that change the sectoral composition of employment in the long run, and those that cause temporary movement of hours. Our identifying restriction exploits the distinctive nature of the two margins of labor: employment and hours per worker. Based on the postwar U.S. data, we find that aggregate and sectoral disturbances are roughly equally important for the cyclical fluctuations of aggregate hours.