Knowledge that Transforms

Researchers often hold out data from the estimation of econometric models to use for external validation. However, the use of holdout samples is suboptimal from a Bayesian perspective, which prescribes using the entire sample to form posterior model weights. This paper examines a possible rationale for the use of holdout samples: data-inspired modifications of structural models are likely to lead to an exaggeration of model fit. The use of holdout samples can, in principle, set an incentive for the modeler not to exaggerate model fit.

A real wage rate is a nominal wage rate divided by the price of a good and is a transparent measure of how much of the good an hour of work buys. It provides an important indicator of the living standards of workers, and also of the productivity of workers. In this paper I set out the conceptual basis for such measures, provide some historical examples, and then provide my own preliminary analysis of a decade long project designed to measure the wages of workers doing the same job in over 60 countries—workers at McDonald's restaurants. The results demonstrate that the wage rates of workers using the same skills and doing the same jobs differ by as much as 10 to 1, and that these gaps declined over the period 2000–2007, but with much less progress since the Great Recession.

We develop a stylized model of economic growth with bubbles in which changes in investor sentiment lead to the appearance and collapse of macroeconomic bubbles or pyramid schemes. These bubbles mitigate the effects of financial frictions. During bubbly episodes, unproductive investors demand bubbles while productive investors supply them. These transfers of resources improve economic efficiency thereby expanding consumption, the capital stock and output. When bubbly episodes end, there is a fall in consumption, the capital stock and output. We argue that the stochastic equilibria of the model provide a natural way of introducing bubble shocks into business cycle models.

A key lesson of the financial crisis 2007-09 is that the Bagehot Rule, “lend freely but at a high rate,” needs to be updated for the emerging market-based credit system. A modern rule is suggested: Markets, not Banks; Outside spread, not Inside spread; Core, not Periphery.

The joint dynamics of US net output, consumption, and (the market value of) foreign assets and liabilities, characterized empirically following Lettau and Ludvigson (2004), is shown to be consistent with current account theory. US consumption is virtually insulated from transitory shocks, while these contribute to variations in net output and gross foreign positions—consumption is smoothed against temporary fluctuations in returns. A single permanent shock—naturally interpreted as a supply shock—raises consumption swiftly while causing net output to adjust gradually. This leads to persistent, procyclical external deficits, while moving gross assets and liabilities in the same direction. JEL: E21, E23, F32, F34

We consider competition between sellers selling multiple distinct products to a buyer having k slots. Under independent pricing, a pure strategy equilibrium often does not exist, and equilibrium in mixed strategy is never efficient. When bundling is allowed, each seller has an incentive to bundle his products, and an efficient “technology-renting” equilibrium always exists. Furthermore, in the case of digital goods or when sales below marginal cost are banned, all equilibria are efficient. Comparing the mixed-strategy equilibrium with the technology-renting equilibrium reveals that bundling often increases the buyer's surplus. Finally, we derive clear-cut policy implications.

What determines reciprocity in employment relations? We conducted a controlled field experiment to measure the extent to which monetary and nonmonetary gifts affect workers' performance. We find that nonmonetary gifts have a much stronger impact than monetary gifts of equivalent value. We also observe that when workers are offered the choice, they prefer receiving money, but reciprocate as if they received a nonmonetary gift. This result is consistent with the common saying, “it's the thought that counts.” We underline this point by showing that monetary gifts can effectively trigger reciprocity if the employer invests more time and effort into the gift's presentation.

We present evidence on the term structure of the equity premium. We recover prices of dividend strips, which are short-term assets that pay dividends on the stock index every period up to period T and nothing thereafter. It is short-term relative to the index because the index pays dividends in perpetuity. We find that expected returns, Sharpe ratios, and volatilities on short-term assets are higher than on the index, while their CAPM betas are below one. Short-term assets are more volatile than their realizations, leading to excess volatility and return predictability. Our findings are inconsistent with many leading theories.

Real matching markets are subject to constraints. For example, the Japanese government introduced a new medical matching system in 2009 that imposes a “regional cap” in each of its 47 prefectures, which regulates the total number of medical residents who can be employed in each region. Based on Kamada and Kojima (2011), this paper studies matching markets with such constraints by examining in great detail the Japanese medical matching market. Specifically, we show that the new system introduced in 2009 has problems in terms of stability and strategy-proofness, and provide an alternative mechanism that does better.

We develop a quality competition model to understand how price controls affect market outcomes in buyer-seller markets with discrete goods of varying quality. While competitive equilibria do not necessarily exist in such markets when price controls are imposed, we show that stable outcomes do exist and characterize the set of stable outcomes in the presence of price restrictions. In particular, we show that price controls induce non-price competition: price floors induce the trade of inefficiently high quality goods, while price ceilings induce the trade of inefficiently low quality goods.