Business start-ups and productive efficiency

This paper studies efficient allocation of resources in an economy in which agents are initially heterogeneous with regard to their wealth levels and whether they have ideas or not. An agent with an idea can start a business that generates random returns. Agents have private information about (1) their initial types, (2) how they allocate their resources, and (3) the realized returns. The unobservability of returns creates a novel motive for subsidizing agents who have ideas but lack resources to invest in them. To analyze this motive in isolation, the paper assumes that agents are risk-neutral and abstracts away from equality and insurance considerations. The unobservability of initial types and actions implies that the subsidy that poor agents with ideas receive is limited by incentive compatibility: the society should provide other agents with enough incentives so that they do not claim to be poor and have ideas. The paper then provides an implementation of the constrained-efficient allocation in an incomplete markets setup that is similar to the U.S. Small Business Administration's Business Loan Program. Finally, the paper extends the model in several dimensions to show that the results are robust to these generalizations of the model.Productivity

A Deterministic Theory for Exact Non-Convex Phase Retrieval

In this paper, we analyze the non-convex framework of Wirtinger Flow (WF) for phase retrieval and identify a novel sufficient condition for universal exact recovery through the lens of low rank matrix recovery theory. Via a perspective in the lifted domain, we show that the convergence of the WF iterates to a true solution is attained geometrically under a single condition on the lifted forward model. As a result, a deterministic relationship between the accuracy of spectral initialization and the validity of {the regularity condition} is derived. In particular, we determine that a certain concentration property on the spectral matrix must hold uniformly with a sufficiently tight constant. This culminates into a sufficient condition that is equivalent to a restricted isometry-type property over rank-1, positive semi-definite matrices, and amounts to a less stringent requirement on the lifted forward model than those of prominent low-rank-matrix-recovery methods in the literature. We characterize the performance limits of our framework in terms of the tightness of the concentration property via novel bounds on the convergence rate and on the signal-to-noise ratio such that the theoretical guarantees are valid using the spectral initialization at the proper sample complexity.Comment: In Revision for IEEE Transactions on Signal Processin

Spatial Distribution of Housing Investment and Perception of Earthquake Risk in Istanbul Metropolitan Area

Istanbul, the largest metropolitan area in Turkey with a population of over 15 million inhabitants, lies close to major and active fault lines and has been previously hit by fatal earthquakes several times. Facing a high seismic risk as forecasted in a number of studies; Istanbul is particularly vulnerable due to the high density of old housing areas in the city center. Although there is a great body of knowledge in the literature focusing on the seismic risk of Istanbul and possible scenarios to strengthen the capacity for emergency preparedness in the event of future earthquakes, the attitudes and perceptions of housing investors living under the threat of the earthquake is yet to be explored. This study is an attempt to address this gap and aims to investigate the relationship between the location of the housing investment and perception of earthquake risk of the investors. Data was collected by means of a questionnaire from 117 participants, who made an investment in housing in Istanbul since 1999 Kocaeli earthquake. ArcGIS is used to indicate the spatial distribution of investment and the results provide empirical evidence of how spatial distribution of housing investment differs depending on the earthquake risk perception of the investors.

Neuroanatomical and Neurochemical Basis of Impulsivity

The term ‘impulsivity’ encompasses a multitude of behaviours that are poorly conceived, premature, inappropriate, and that frequently result in unwanted or deleterious outcomes. Impulsivity manifests as impatience carelessness, risk-taking, sensation-seeking and pleasure-seeking, an underestimated sense of harm, and extroversion. Impulsivity is a core symptom of a broad spectrum of psychiatric disorders. Through focusing on different aspects of impulsive behavior, it has proved possible to devise a variety of behavioral paradigms to measure impulsivity in both human and non-human subjects. These can be broadly divided into two categories: those measuring impulsive action or motoric impulsivity, and those measuring impulsive choice or impulsive decision-making. Impulsive action can be broadly defined as the inability to withhold from making a response. Within the framework of behavioral neuroscience and cognitive psychology, impulse control has been described as an active inhibitory mechanism which modulates the internally or externally driven pre-potent desire for primary reinforcers such as food, sex or other highly desirable rewards. This inhibitory control mechanism may provide the substrate by which rapid conditioned responses and reflexes are transiently suppressed, so that slower cognitive mechanisms can guide behavior. This process is referred to as response inhibition. Two of the most common tests used to study inhibitory processes are the go/no-go and stop-signal reaction time tasks. Impulsivity is also evident in the making of impulsive decisions or choices as well as in impulsive actions. Here, there is no “pre-potent” response that is primed and then forcibly inhibited, but a decision-making processes. Impulsive decision making or impulsive choice is defined as initiating actions without adequately considering other possible choices or consequences. Impulsive choice is typically measured in the delay discounting paradigm. In tis paradigm, the tendency to prefer small immediate rewards over larger, more delayed reinforcers is measured. İmpulsive choice is defined by a greater tendency to value or choose smaller, more immediate reinforcers. Impulsivity is a multi-faceted behaviour. This behaviour may be studied by subdividing it into different processes neuroanatomically and neurochemically. Neuroanatomical data support the suggestion that behavioral disinhibition (impulsive action / motoric impulsivity) and delay-discounting (impulsive choice / decision making) differ in the degree to which various components of frontostriatal loops are implicated in their regulation. The dorsal prefrontal cortex does not appear to be involved in mediating impulsive choice, yet does have some role in regulating inhibitory processes. In contrast, there appears to be a pronounced role for the orbitofrontal cortex and basolateral amygdala in controlling impulsive choice. Other structures, however, such as the nucleus accumbens and subthalamic nucleus may be common to both circuits. From the neurochemical perspective, dopamine system and dopamine- 2 (D2) receptors in particular, seems to be closely involved in making impulsive choice. When the noradrenaline system does not function optimally, it might contribute to increased impulsivity. Serotonin might act upon prefrontal cortex to decrease impulsive choices. Interactions between the serotonin and the dopamine systems are important in the regulation of impulsive behaviour. It is possible that various receptor subtypes of the serotonin system may exert differing and even contrasting effects on impulsive behaviour. Although it is very informative to study neurotransmitter systems separately, it should be kept in mind that there are very intimate interactions between the neurotransmitter systems mentioned above. Based on the fact that impulsivity is regulated through multiple neurotransmitters and even more receptors, one may suggest that pharmacotherapy of impulsivity requires a drug acting on more than one receptor. In addition, when considering improving impulsivity for the treatment of a psychiatric disorder, it is always necessary to know which type of impulsive behaviour exists in that particular disorder. Hence, improving impulsivity for the treatment of psychiatric disorders requires tailoring of pharmacological agents in a precise and perhaps in an individualized manner