Silvana Tenreyro

THE LOG OF GRAVITY

Although economists have long been aware of Jensens inequality, many econometric applications have neglected an important implication of it: the standard practice of interpreting the parameters of log-linearized models estimated by ordinary least squares as elasticities can be highly misleading in the presence of heteroskedasticity. This paper explains why this problem arises and proposes an appropriate estimator. Our criticism of conventional practices and the solution we propose extends to a broad range of economic applications where the equation under study is log-linearized. We develop the argument using one particular illustration, the gravity equation for trade, and apply the proposed technique to provide new estimates of this equation. We find significant differences between estimates obtained with the proposed estimator and those obtained with the traditional method.

The Log of Gravity

Although economists have long been aware of Jensens inequality, many econometric applications have neglected an important implication of it: under heteroskedasticity, the parameters of log-linearized models estimated by OLS lead to biased estimates of the true elasticities. We explain why this problem arises and propose an appropriate estimator. Our criticism of conventional practices and the proposed solution extend to a broad range of applications where log-linearized equations are estimated. We develop the argument using one particular illustration, the gravity equation for trade. We find significant differences between estimates obtained with the proposed estimator and those obtained with the traditional method.

On the Trade Impact of Nominal Exchange Rate Volatility

What is the effect of nominal exchange rate variability on trade? I argue that the methods conventionally used to answer this perennial question are plagued by a variety of sources of systematic bias. I propose a novel approach that simultaneously addresses all of these biases, and present new estimates from a broad sample of countries from 1970 to 1997. The answer to the question is: Not much.

The Timing of Monetary Policy Shocks

A vast empirical literature has documented delayed and persistent effects of monetary policy shocks on output. We show that this finding results from the aggregation of output impulse responses that differ sharply depending on the timing of the shock: When the monetary policy shock takes place in the first two quarters of the year, the response of output is quick, sizable, and dies out at a relatively fast pace. In contrast, output responds very little when the shock takes place in the third or fourth quarter. We propose a potential explanation for the differential responses based on uneven staggering of wage contracts across quarters. Using a stylized dynamic general equilibrium model, we show that a very modest amount of uneven staggering can generate differences in output responses similar to those found in the data.

Trading Partners and Trading Volumes:Implementing the Helpman-Melitz-Rubinstein Model Empirically

Helpman, Melitz and Rubinstein [Quarterly Journal of Economics (2008) Vol. 123, pp. 441–487] (HMR) present a rich theoretical model to study the determinants of bilateral trade flows across countries. The model is then empirically implemented through a two-stage estimation procedure. We argue that this estimation procedure is only valid under the strong distributional assumptions maintained in the article. Statistical tests using the HMR sample, however, clearly reject such assumptions. Moreover, we perform numerical experiments which show that the HMR two-stage estimator is very sensitive to departures from the assumption of homoskedasticity. These findings cast doubts on any inference drawn from the empirical implementation of the HMR model.

Wage Setting Patterns and Monetary Policy: International Evidence

Systematic differences in the timing of wage setting decisions among industrialized countries provide an ideal framework to study the importance of wage rigidity in the transmission of monetary policy. The Japanese Shunto presents the best-known case of bunching in wage setting decisions: From February to May, most firms set wages that remain in place until the following year; wage rigidity, thus, is relatively higher immediately after the Shunto. Similarly, in the United States, a large fraction of firms adjust wages in the last quarter of the calendar year. In contrast, wage agreements in Germany are well spread within the year, implying a relatively uniform degree of rigidity. We exploit variation in the timing of wage setting decisions within the year in Japan, the United States, Germany, the United Kingdom, and France to investigate the effects of monetary policy under different degrees of effective wage rigidity. Our findings lend support to the long-held, though scarcely tested, view that wage rigidity plays a key role in the transmission of monetary policy.

Gravity-defying trade

Heteroskedasticity and the existence of zero values in bilateral-trade data lead to significant biases in standard estimations of the gravity equation. We propose a new estimation technique that addresses these problems, and provide novel estimates of the gravity equation. Three results stand out. First, contrary to general belief, income elasticities are significantly smaller than 1, suggesting modifications to standard trade models. Second, simple estimators of the gravity equation greatly exaggerate the roles of distance and colonial links. Finally, bilateral trade between countries that have signed a free-trade agreement is 30 percent larger than that between other countries, a magnitude remarkably different from that predicted by conventional methods (above 100 percent).

Testing competing models for non-negative data with many zeros

Abstract In economic applications it is often the case that the variate of interest is non-negative and its distribution has a mass-point at zero. Many regression strategies have been proposed to deal with data of this type but, although there has been a long debate in the literature on the appropriateness of different models, formal statistical tests to choose between the competing specifications are not often used in practice. We use the non-nested hypothesis testing framework of Davidson and MacKinnon (Davidson and MacKinnon 1981. “Several Tests for Model Specification in the Presence of Alternative Hypotheses.” Econometrica 49: 781–793.) to develop a novel and simple regression-based specification test that can be used to discriminate between these models.

Commodity booms and busts in emerging economies

Emerging economies, particularly those dependent on commodity exports, are prone to highly disruptive economic cycles. This paper proposes a small open economy model for a net commodity exporter to quantitatively study the triggers of these cycles. The economy consists of two sectors, one of which produces commodities with prices subject to exogenous international fluctuations. These fluctuations affect both the competitiveness of the economy and its borrowing terms, as higher commodity prices are associated with lower spreads between the countrys borrowing rate and world interest rates. Both effects jointly result in strongly positive effects of commodity price increases on GDP, consumption, and investment, and a negative effect on the total trade balance. Furthermore, they generate excess volatility of consumption over output and a large volatility of investment. Besides explicitly incorporating a double role of commodity prices, the model structure nests the various candidate sources of shocks proposed in previous work on emerging economy business cycles. Estimating the model on Argentine data, we find that the contribution of commodity price shocks to fluctuations in post-1950 output growth is in the order of 38%. In addition, commodity prices account for around 42% and 61% of the variation in consumption and investment growth, respectively. We find transitory productivity shocks to be an important driver of output fluctuations, exceeding the contribution of shocks to the trend, which, though smaller, is not negligible

History dependence in the housing market

Using the universe of housing transactions in England and Wales in the last twenty years, we document a robust pattern of history dependence in housing markets. Sale prices and selling probabilities today are affected by aggregate house prices prevailing in the period in which properties were previously bought. We investigate the causes of history dependence, with its quantitative implications for the post-crisis recovery of the housing market. To do so we complement our analysis with administrative data on mortgages and online house listings, which we match to actual sales. We find that high leverage in the pre-crisis period and anchoring (or reference dependence) both contributed to the collapse and slow recovery of the volume of housing transactions. We find no asymmetric effects of anchoring to previous prices on current transactions; in other words, loss aversion does not appear to play a role over and above simple anchoring.