Start-up costs and pecuniary externalities as barriers to economic development

We use a dynamic monopolistic competition model to show that an economythat inherits a small range of specialized inputs can be trapped into alower stage of development. The limited availability of specialized inputsforces the final goods producers to use a labor intensive technology, whichin turn implies a small inducement to introduce new intermediate inputs. Thestart--up costs, which make the intermediate inputs producers subject todynamic increasing returns, and pecuniary externalities that result from thefactor substitution in the final goods sector, play essential roles in themodel.

Bubbly collateral and economic activity

This paper develops a model of the bubbly economy and uses it to study the effects of bailoutpolicies. In the bubbly economy, weak enforcement institutions do not allow firms to pledge futurerevenues to their creditors. As a result, "fundamental" collateral is scarce and this impairs the intermediationprocess that transforms savings into capital. To overcome this shortage of "fundamental"collateral, the bubbly economy creates "bubbly" collateral. This additional collateral supports anintricate array of intra- and inter-generational transfers that allow savings to be transformed intocapital and bubbles. Swings in investor sentiment lead to fluctuations in the amount of bubblycollateral, giving rise to bubbly business cycles with very rich and complex dynamics.Bailout policies can affect these dynamics in a variety of ways. Expected bailouts provideadditional collateral and expand investment and the capital stock. Realized bailouts reduce thesupply of funds and contract investment and the capital stock. Thus, bailout policies tend to fosterinvestment and growth in normal times, but to depress investment and growth during crisis periods.We show how to design bailout policies that maximize various policy objectives.

Measuring time-varying economic fears with consumption-based stochastic discount factors

This paper analyzes empirically the volatility of consumption-based stochastic discount factors as a measure of implicit economic fears by studying its relationship with future economic and stock market cycles. Time-varying economic fears seem to be well captured by the volatility of stochastic discount factors. In particular, the volatility of recursive utility-based stochastic discount factor with contemporaneous growth explains between 9 and 34 percent of future changes in industrial production at short and long horizons respectively. They also explain ex-ante uncertainty and risk aversion. However, future stock market cycles are better explained by a similar stochastic discount factor with long-run consumption growth. This specification of the stochastic discount factor presents higher volatility and lower pricing errors than the specification with contemporaneous consumption growth.

25-hydroxyvitamin D concentration is inversely associated with serum MMP-9 in a cross-sectional study of African American ESRD patients.

BACKGROUND: Circulating 25-hydroxyvitamin D [25(OH)D] concentration is inversely associated with peripheral arterial disease and hypertension. Vascular remodeling may play a role in this association, however, data relating vitamin D level to specific remodeling biomarkers among ESRD patients is sparse. We tested whether 25(OH)D concentration is associated with markers of vascular remodeling and inflammation in African American ESRD patients.METHODS: We conducted a cross-sectional study among ESRD patients receiving maintenance hemodialysis within Emory University-affiliated outpatient hemodialysis units. Demographic, clinical and dialysis treatment data were collected via direct patient interview and review of patients records at the time of enrollment, and each patient gave blood samples. Associations between 25(OH)D and biomarker concentrations were estimated in univariate analyses using Pearson's correlation coefficients and in multivariate analyses using linear regression models. 25(OH) D concentration was entered in multivariate linear regression models as a continuous variable and binary variable (<15 ng/ml and =15 ng/ml). Adjusted estimate concentrations of biomarkers were compared between 25(OH) D groups using analysis of variance (ANOVA). Finally, results were stratified by vascular access type.RESULTS: Among 91 patients, mean (standard deviation) 25(OH)D concentration was 18.8 (9.6) ng/ml, and was low (<15 ng/ml) in 43% of patients. In univariate analyses, low 25(OH) D was associated with lower serum calcium, higher serum phosphorus, and higher LDL concentrations. 25(OH) D concentration was inversely correlated with MMP-9 concentration (r = -0.29, p = 0.004). In multivariate analyses, MMP-9 concentration remained negatively associated with 25(OH) D concentration (P = 0.03) and anti-inflammatory IL-10 concentration positively correlated with 25(OH) D concentration (P = 0.04).CONCLUSIONS: Plasma MMP-9 and circulating 25(OH) D concentrations are significantly and inversely associated among ESRD patients. This finding may suggest a potential mechanism by which low circulating 25(OH) D functions as a cardiovascular risk factor.

Catalan government popularity. An example of economic effects on sub-national government support

The aim of this essay is to deal with economic voting in contexts ofmultilevel governance and to be a contribution to the debate on attribution of responsibilities in popularity functions literature. We use aggregate and individual data from Catalonia in order to analyse the relation between the state of the economy and the support for a sub-state government. The empirical analysis shows that the responsibility hypothesis works in regional governments without explicit macroeconomic competencies. We have also considered the evaluations of government performance on certain specific policies in order to clarify and determine the factors that drive Catalan government support. The article considers the implications of the findings for future attempts to model party support in a context of the European Union.

Subcontracting and vertical integration in the Spanish cotton industry

This paper examines changes in the organization of the Spanish cotton industry from 1720 to 1860 in its core region of Catalonia. As the Spanish cotton industry adopted the most modern technology and experienced the transition to the factory system, cotton spinning and weaving mills became increasingly vertically integrated. Asset specificity more than other factors explained this tendency towards vertical integration. The probability for a firm of being vertically integrated was higher among firms located in districts with high concentration ratios and rose with size and the use of modern machinery. Simultaneously, subcontracting predominated in other phases of production and distribution where transaction costs appears to be less important.

Motivation, test scores and economic success

This paper argues that low-stakes test scores, available in surveys, may be partially determinedby test-taking motivation, which is associated with personality traits but not with cognitiveability. Therefore, such test score distributions may not be informative regarding cognitiveability distributions. Moreover, correlations, found in survey data, between high test scoresand economic success may be partially caused by favorable personality traits. To demonstratethese points, I use the coding speed test that was administered without incentives to NationalLongitudinal Survey of Youth 1979 (NLSY) participants. I suggest that due to its simplicityits scores may especially depend on individuals' test-taking motivation. I show that controllingfor conventional measures of cognitive skills, the coding speed scores are correlated with futureearnings of male NLSY participants. Moreover, the coding speed scores of highly motivated,though less educated, population (potential enlists to the armed forces) are higher than NLSYparticipants' scores. I then use controlled experiments to show that when no performance-basedincentives are provided, participants' characteristics, but not their cognitive skills, affect effortinvested in the coding speed test. Thus, participants with the same ability (measured by theirscores on an incentivized test) have significantly different scores on tests without performance-based incentives.

Determinants of economic growth: Will data tell?

Many factors inhibiting and facilitating economic growth havebeen suggested. Can agnostics rely on international incomedata to tell them which matter? We find that agnostic priorslead to conclusions that are sensitive to differences acrossavailable income estimates. For example, the PWT 6.2 revisionof the 1960-96 income estimates in the PWT 6.1 leads tosubstantial changes regarding the role of government,international trade, demography, and geography. We concludethat margins of error in international income estimates appeartoo large for agnostic growth empirics.

Economic growth and investment in the Arab world

This paper analyses the economic growth performance in the Arab world overthe last forty years. The Arab world has managed to reduce povertyperformance despite its relatively disappointing growth performance. Werelate this poor performance of both oil and non-oil producers toinvestment. Contrary to widespread belief, we do not find evidence that lowquantity of investment is the main of low growth. The decline in theinvestment rate followed rather than preceded the reduction in the aggregategrowth rate. We conclude that the low quality of investment projects is thekey determinant of growth. The excessive reliance on public investment, thelow quality of financial institutions, the bad business environment (due topolitical and social instability and to excessive public intervention andoverregulation) and the low quality of human capital are importantdeterminants of systematically unproductive investment decisions and, thus,low economic growth.

Dynamics of the control of Aedes (Stegomyia) aegypti Linnaeus (Diptera, Culicidae) by Bacillus thuringiensis var israelensis, related with temperature, density and concentration of insecticide

The dynamics of the control of Aedes (Stegomyia) aegypti Linnaeus, (Diptera, Culicidae) by Bacillus thuringiensis var israelensis has been related with the temperature, density and concentration of the insecticide. A mathematical model for biological control of Aedes aegypti with Bacillus thuringiensis var israelensis (Bti) was constructed by using data from the literature regarding the biology of the vector. The life cycle was described by differential equations. Lethal concentrations (LC50 and LC95) of Bti were determined in the laboratory under different experimental conditions. Temperature, colony, larvae density and bioinsecticide concentration presented marked differences in the analysis of the whole set of variables; although when analyzed individually, only the temperature and concentration showed changes. The simulations indicated an inverse relationship between temperature and mosquito population, nonetheless, faster growth of populations is reached at higher temperatures. As conclusion, the model suggests the use of integrated control strategies for immature and adult mosquitoes in order to achieve a reduction of Aedes aegypti.

A sharp concentration inequality with applications

We present a new general concentration-of-measure inequality and illustrate its power by applications in random combinatorics. The results find direct applications in some problems of learning theory.

Responsiveness of astrocytes in serum-free aggregate cultures to epidermal growth factor: dependence on the cell cycle and the epidermal growth factor concentration.

Serum-free aggregating cell cultures of fetal rat telencephalon treated with low doses (0.5 nM) of epidermal growth factor (EGF) showed a small, transient increase in DNA synthesis but no significant changes in total DNA and protein content. By contrast, treatment with high doses (13 nM) of EGF caused a marked stimulation of DNA synthesis as well as a net increase in DNA and protein content. The expression of the astrocyte-specific enzyme, glutamine synthetase, was greatly enhanced both at low and at high EGF concentrations. These results suggest that at low concentration EGF stimulates exclusively the differentiation of astrocytes, whereas at high concentration, EGF has also a mitogenic effect. Nonproliferating astrocytes in cultures treated with 0.4 microM 1-beta-D-arabinofuranosyl-cytosine were refractory to EGF treatment, indicating that their responsiveness to EGF is cell cycle-dependent. Binding studies using a crude membrane fraction of 5-day cultures showed a homogeneous population of EGF binding sites (Kd approximately equal to 2.6 nM). Specific EGF binding sites were found also in non-proliferating (and nonresponsive) cultures, although they showed slightly reduced affinity and binding capacity. This finding suggests that the cell cycle-dependent control of astroglial responsiveness to EGF does not occur at the receptor level. However, it was found that the specific EGF binding sites disappear with progressive cellular differentiation.