A Constrained L1 Minimization Approach to Sparse Precision Matrix Estimation

A constrained L1 minimization method is proposed for estimating a sparse inverse covariance matrix based on a sample of $n$ iid $p$-variate random variables. The resulting estimator is shown to enjoy a number of desirable properties. In particular, it is shown that the rate of convergence between the estimator and the true $s$-sparse precision matrix under the spectral norm is $s\sqrt{\log p/n}$ when the population distribution has either exponential-type tails or polynomial-type tails. Convergence rates under the elementwise $L_{\infty}$ norm and Frobenius norm are also presented. In addition, graphical model selection is considered. The procedure is easily implementable by linear programming. Numerical performance of the estimator is investigated using both simulated and real data. In particular, the procedure is applied to analyze a breast cancer dataset. The procedure performs favorably in comparison to existing methods.Comment: To appear in Journal of the American Statistical Associatio

Private Information, Growth and Asset Prices with Stochastic Disturbances

We introduce both idiosyncratic and aggregate shocks in an endogenous growth model with endogenous partial insurance to the idiosyncratic shock. Aggregate uncertainty introduces an additional channel that can play an important role in determining the effects of private information on expected growth and asset prices. We show the impact of aggregate and idiosyncratic shocks on expected growth and on the variability of individual quantities and asset prices.optimal contract, endogenous growth, endogenous partial insurance, asset prices

Is small-scale agriculture really the main driver of deforestation in the Peruvian Amazon? Moving beyond the prevailing narrative

A key premise underlying discussion about deforestation in Amazonian Peru is that small-scale or so-called migratory agriculture is the main driver of deforestation. This premise has been expressed in government documents and public outreach events. How the Peruvian government understands drivers of deforestation in the Amazon has profound implications for how it will confront the problem. It is therefore important to critically revisit assumptions under-lying this narrative. We find that the narrative is based on remote sensing of deforestation patch sizes but not on field data, potentially conflating distinct drivers of deforestation under the umbrella of “migratory,” “small-scale,” or “subsistence” agriculture. In fact, small patches of deforested land may indicate any number of processes, including sustainable fallow management and agroforestry. Moreover, the data underlying the narrative tell us little about the actors driving these processes or their motivations. Different pro-cesses have distinct implications for environmental sustainability and require targeted policy responses. We unpack these diverse actors, geographies, and motivations of small-patch deforestation in the Peruvian Amazon and argue that differentiating among these drivers is necessary to develop appropriate policy responses. We call for researchers to revisit assumptions and critically assess the motivations of observed deforestation to appropriately target policy action

Optimal fiscal policy, public capital, and the productivity slowdown

A presentation of a quantitative-theoretical model that can account for much of the behavior of the stock of public capital in the U.S. economy over the last 70 years, with an application to examining some possible causes of the slowdown in the growth of U.S. labor productivity.Capital ; Fiscal policy ; Labor productivity

IMAGES I. Strong evolution of galaxy kinematics since z=1

(abbreviated) We present the first results of the ESO large program, ``IMAGES'' which aims at obtaining robust measurements of the kinematics of distant galaxies using the multi-IFU mode of GIRAFFE on the VLT. 3D spectroscopy is essential to robustly measure the often distorted kinematics of distant galaxies (e.g., Flores et al. 2006). We derive the velocity fields and $\sigma$-maps of 36 galaxies at 0.4<z<0.75 from the kinematics of the [OII] emission line doublet, and generate a robust technique to identify the nature of the velocity fields based on the pixels of the highest signal-to-noise ratios (S/N). We have gathered a unique sample of 63 velocity fields of emission line galaxies (W0([OII]) > 15 A) at z=0.4-0.75, which are a representative subsample of the population of M_stellar>1.5x10^{10} M_sun emission line galaxies in this redshift range, and are largely unaffected by cosmic variance. Taking into account all galaxies -with or without emission lines- in that redshift range, we find that at least 41+/-7% of them have anomalous kinematics, i.e., they are not dynamically relaxed. This includes 26+/-7% of distant galaxies with complex kinematics, i.e., they are not simply pressure or rotationally supported. Our result implies that galaxy kinematics are among the most rapidly evolving properties, because locally, only a few percent of the galaxies in this mass range have complex kinematics.Comment: 17 pages, 6 figures, Accepted by A&

Concerning Technology Adoption and Inequality

Empirical evidence suggests that there has been a divergence over time in income distributions across countries and within countries. Furthermore, developing economies show a great deal of diversity in their growth patterns during the process of economic development. For example, some of these countries converge rapidly on the leaders, while others stagnate, or even experience reversals and declines in their growth processes. In this paper we study a simple dynamic general equilibrium model with household specific costs of technology adoption which is consistent with these stylized facts. In our model, growth is endogenous, and there are two-period lived overlapping generations of agents, assumed to be heterogeneous in their initial holdings of wealth and capital. We find that in a special case of our model, with costs associated with the adoption of more productive technologies fixed across households, inequalities in wealth and income may increase over time, tending to delay the convergence in international income differences. The model is also capable of explaining some of the observed diversity in the growth pattern of transitional economies. According to the model, this diversity may be the result of variability in adoption costs over time, or the relative position of a transitional economy in the world income distribution. In the more general case of the model with household specific adoption costs, negative growth rates during the transitional process are also possible. The model’s prediction that inequality has negative impact on technology adoption is supported by empirical evidence based on a cross country data set.inequality, technology adoption, international income differences, altruism, negative growth rates.

Public Infrastructure Spillovers and Growth: Theory and Time Series Evidence for Australia.

In this paper, growth of per capita income can be exogenous and/or endogenous due to aggregate public infrastructure spillover. The deterministic Glomm and Ravikumar (1994) model is augmented in this paper to produce a stochastic growth counterpart which has useful time series implications.INCOME ; TIME SERIES ; CAPITAL