Hit or Miss? The Effect of Assassinations on Institutions and War

Assassinations are a persistent feature of the political landscape. Using a new data set of assassination attempts on all world leaders from 1875 to 2004, we exploit inherent randomness in the success or failure of assassination attempts to identify assassination's effects. We find that, on average, successful assassinations of autocrats produce sustained moves toward democracy. We also find that assassinations affect the intensity of small-scale conflicts. The results document a contemporary source of institutional change, inform theories of conflict, and show that small sources of randomness can have a pronounced effect on history.

The Anatomy of Start-Stop Growth

This paper investigates the remarkable extremes of growth experiences within countries and examines the changes that occur when growth starts and stops. We find three main results. First, all but the very richest countries experience both growth miracles and failures over substantial periods. Second, growth accounting reveals that physical capital accumulation plays a negligible role in growth take-offs and a larger but still modest role in growth collapses. The implied role of productivity in these shifts is also directly reflected in employment reallocations and changes in trade. Third, growth accelerations and collapses are asymmetric phenomena. Collapses typically feature reduced manufacturing and investment amidst increasing price instability, whereas growth takeoffs are primarily associated with large and steady expansions in international trade. This asymmetry suggests that the roads into and out of rapid growth expansions may not be the same. The results stand in contrast to much growth theory and conventional wisdom: despite much talk of poverty traps, even very poor countries regularly grow rapidly, and the role of aggregate investment in growth accelerations is negligible.

Acoustic scattering of broadband echolocation signals from prey of Blainville's beaked whales : modeling and analysis

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2006Blainville's beaked whales (Mesoplodon densirostris) use broadband, ultrasonic echolocation signals (27 to 57 kHz) to search for, localize, and approach prey that generally consist of mid-water and deep-water fishes and squid. Although it is well known that the spectral characteristics of broadband echoes from marine organisms are a strong function of size, shape, orientation and anatomical group, little is known as to whether or not these or other toothed whales use spectral cues in discriminating between prey and non-prey. In order to study the prey-classification process, a stereo acoustic tag was mounted on a Blainville's beaked whale so that emitted clicks and corresponding echoes from prey could be recorded. A comparison of echoes from prey selected by the whale and those from randomly chosen scatterers suggests that the whale may have, indeed, discriminated between echoes using spectral features and target strengths. Specifically, the whale appears to have favored prey with one or more deep nulls in the echo spectra as well as ones with higher target strength. A three-dimensional, acoustic scattering model is also developed to simulate broadband scattering from squid, a likely prey of the beaked whale. This model applies the distorted wave Born approximation (DWBA) to a weakly-scattering, inhomogeneous body using a combined ray trace and volume integration approach. Scatterer features are represented with volume elements that are small (less than 1/12th of the wavelength) for the frequency range of interest (0 to 120 kHz). Ranges of validity with respect to material properties and numerical considerations are explored using benchmark computations with simpler geometries such as fluid-filled spherical and cylindrical fluid shells. Modeling predictions are compared with published data from live, freely swimming squid. These results, as well as previously published studies, are used in the analysis of the echo spectra of the whale's ensonified targets

Preparing pseudo-pure states with controlled-transfer gates

The preparation of pseudo-pure states plays a central role in the implementation of quantum information processing in high temperature ensemble systems, such as nuclear magnetic resonance. Here we describe a simple approach based on controlled-transfer gates which permits pseudo-pure states to be prepared efficiently using spatial averaging techniques.Comment: Significantly revised and extended: now 7 pages including 3 figures; Phys. Rev. A (in press

Quantum Information Processing with Delocalized Qubits under Global Control

Any technology for quantum information processing (QIP) must embody within it quantum bits (qubits) and maintain control of their key quantum properties of superposition and entanglement. Typical QIP schemes envisage an array of physical systems, such as electrons or nuclei, with each system representing a given qubit. For adequate control, systems must be distinguishable either by physical separation or unique frequencies, and their mutual interactions must be individually manipulable. These difficult requirements exclude many nanoscale technologies where systems are densely packed and continuously interacting. Here we demonstrate a new paradigm: restricting ourselves to global control pulses we permit systems to interact freely and continuously, with the consequence that qubits can become delocalized over the entire device. We realize this using NMR studies of three carbon-13 nuclei in alanine, demonstrating all the key aspects including a quantum mirror, one- and two-qubit gates, permutation of densely packed qubits and Deutsch algorithms.Comment: 4 pages, 5 figure

Climate Shocks and Exports

This paper uses international trade data to examine the effects of climate shocks on economic activity. We examine panel models relating the annual growth rate of a country’s exports in a particular product category to the country’s weather in that year. We find that a poor country being 1 degree Celsius warmer in a given year reduces the growth rate of that country’s exports by between 2.0 and 5.7 percentage points, with no detectable effects in rich countries. We find negative effects of temperature on exports of both agricultural products and light manufacturing products, with little apparent effects on heavy industry or raw materials. The results confirm large negative effects of temperature on poor countries’ economies and suggest that temperature affects a much wider range of economic activity than conventionally thought.

What Do We Learn from the Weather? The New Climate-Economy Literature

A rapidly growing body of research applies panel methods to examine how temperature, precipitation, and windstorms influence economic outcomes. These studies focus on changes in weather realizations over time within a given spatial area and demonstrate impacts on agricultural output, industrial output, labor productivity, energy demand, health, conflict, and economic growth, among other outcomes. By harnessing exogenous variation over time within a given spatial unit, these studies help credibly identify (i) the breadth of channels linking weather and the economy, (ii) heterogeneous treatment effects across different types of locations, and (iii) nonlinear effects of weather variables. This paper reviews the new literature with two purposes. First, we summarize recent work, providing a guide to its methodologies, datasets, and findings. Second, we consider applications of the new literature, including insights for the "damage function" within models that seek to assess the potential economic effects of future climate change

The Local Labor Market Impacts of US Megafires

As we learn to sustainably coexist with wildfire, there is an urgent need to improve our understanding of its multidimensional impacts on society. To this end, we undertake a nationwide study to estimate how megafires (wildfires \u3e 100,000 acres in size) affect US labor market outcomes in communities located within the flame zone. Both year-of-fire and over-time dynamic impacts are studied between 2010−2017. We find that counties located within a megafire flame zone experience significantly lower per capita wage earnings across multiple sources of earnings data for up to two years after megafire event occurrence. We find preliminary evidence that impacts are nonlinear over megafire size. These results highlight a new dimension of megafire impacts and expand the scope of the potential costs of megafires that should be considered in benefit-cost analyses of wildfire control and suppression decisions, especially along sustainability dimensions

Climate Change and Economic Growth: Evidence from the Last Half Century

This paper uses annual variation in temperature and precipitation over the past 50 years to examine the impact of climatic changes on economic activity throughout the world. We find three primary results. First, higher temperatures substantially reduce economic growth in poor countries but have little effect in rich countries. Second, higher temperatures appear to reduce growth rates in poor countries, rather than just the level of output. Third, higher temperatures have wide-ranging effects in poor nations, reducing agricultural output, industrial output, and aggregate investment, and increasing political instability. Analysis of decade or longer climate shifts also shows substantial negative effects on growth in poor countries. Should future impacts of climate change mirror these historical effects, the negative impact on poor countries may be substantial.

Temperature and Income: Reconciling New Cross-Sectional and Panel Estimates

This paper presents novel evidence and analysis of the relationship between temperature and income. First, using sub-national data from 12 countries in the Americas, we provide new evidence that the negative cross-country relationship between temperature and income also exists within countries and even within states. Second, we provide a theoretical framework for reconciling the substantial, negative association between temperature and income in the cross-section with the even stronger short-run effects of temperature estimated by panel models. The theoretical framework suggests that half of the negative short-term effects of temperature may be offset in the long run through adaptation.