A Framework for Realistic and Systematic Multicast Performance Evaluation

Previous multicast research often makes commonly accepted but unverifed assumptions on network topologies and group member distribution in simulation studies. In this paper, we propose a framework to systematically evaluate multicast performance for different protocols. We identify a series of metrics, and carry out extensive simulation studies on these metrics with different topological models and group member distributions for three case studies. Our simulation results indicate that realistic topology and group membership models are crucial to accurate multicast performance evaluation. These results can provide guidance for multicast researchers to perform realistic simulations, and facilitate the design and development of multicast protocols.

The Long-Run Relationship between Money, Nominal GDP, and the Price Level in Venezuela: 1950 to 1996

This paper explores whether a significant long-run relationship exists between money and nominal GDP and between money and the price level in the Venezuelan economy. We apply time-series econometric techniques to annual data for the Venezuelan economy for 1950 to 1996. An important feature of our analysis is the use of tests for unit roots and cointegration with structural breaks. Certain characteristics of the Venezuelan experience suggest that structural breaks may be important. Since the economy depends heavily on oil revenue, oil price shocks have had important influences on most macroeconomic variables. Also since the economy possesses large foreign debt, the world debt crisis that exploded in 1982 had pervasive effects on the Venezuelan economy. Radical changes in economic policy and political instability may have also significantly affected the movement of the macroeconomy. We find that a long-run relationship exists between narrow money (M1) and nominal GDP, the GDP deflator, and the CPI when one makes allowances for one or two structural breaks. We do not find such long-run relationships when broad money (M2) is used.

The Level of Development and the Determinants of Productivity Growth

We examine the effects of technology on productivity growth by disaggregating total output into sectoral components, exploring the roles of investment and technology on productivity growth for countries in different income groups. We find that for low-income countries, investment is the most important determinant of productivity growth. While investment plays an important role in determining productivity growth in middle-income countries, additional effects resulting from technological change also emerge. Investment ceases to have a significant effect on productivity growth in high-income countries.

Where Can Sea Level Rise?

There are some places along Connecticut's coast where marshes have a place to migrate as sea level rises.

The Congressional Budget Process and the Aggregate Level of Spending

This paper analyzes whether the Congressional budget process (instituted in 1974) leads to lower aggregate spending than does the piece-meal appropriations process that preceded it. Previous theoretical analysis, using spatial models of legislator preferences, is inconclusive. This paper uses a model of interest group lobbying, where a legislature determines spending on a national public good and on subsidies to subsets of the population that belong to nationwide sector-specific interest groups. In the appropriations process, the Appropriations Committee proposes a budget, maximizing the joint welfare of voters and the interest groups, that leads to overspending on subsidies. In the budget process, a Budget Committee proposes an aggregate level of spending (the budget resolution); the Appropriations Committee then proposes a budget. If the lobby groups are not subject to a binding resource constraint, the two institutional structures lead to identical outcomes. With such a constraint, however, there is a free rider problem among the groups in lobbying the Budget Committee, as each group only obtains a small fraction of the benefits from increasing the aggregate budget. If the number of groups is sufficiently large, each takes the budget resolution as given, and lobbies only the Appropriations Committee. The main results are that aggregate spending is lower, and social welfare higher, under the budget process; however, provision of the public good is suboptimal. The paper also presents two extensions: the first endogenizes the enforcement of the budget resolution by incorporating the relevant procedural rules into the model. The second analyzes statutory budget rules that limit spending levels, but can be revised by a simple majority vote. In each case,the free rider problem prevents the groups from securing the required changes to procedural and budget rules.

Determinants and Effects of Maturity Mismatches in Emerging Markets: Evidence from Bank Level Data

Despite the extensive work on currency mismatches, research on the determinants and effects of maturity mismatches is scarce. In this paper I show that emerging market maturity mismatches are negatively affected by capital inflows and price volatilities. Furthermore, I find that banks with low maturity mismatches are more profitable during crisis periods but less profitable otherwise. The later result implies that banks face a tradeoff between higher returns and risk, hence channeling short term capital into long term loans is caused by cronyism and implicit guarantees rather than the depth of the financial market. The positive relationship between maturity mismatches and price volatility, on the other hand, shows that the banks of countries with high exchange rate and interest rate volatilities can not, or choose not to hedge themselves. These results follow from a panel regression on a data set I constructed by merging bank level data with aggregate data. This is advantageous over traditional studies which focus only on aggregate data.

Technical Efficiency in the Indian Textiles Industry: A Nonparametric Analysis of Firm-Level Data

The Indian textiles industry is now at the crossroads with the phasing out of quota regime that prevailed under the Multi-Fiber Agreement (MFA) until the end of 2004. In the face of a full integration of the textiles sector in the WTO, maintaining and enhancing productive efficiency is a precondition for competitiveness of the Indian firms in the new liberalized world market. In this paper we use data obtained from the Annual Survey of Industries for a number of years to measure the levels of technical efficiency in the Indian textiles industry at the firm level. We use both a grand frontier applicable to all firms and a group frontier specific to firms from any individual state, ownership, or organization type in order to evaluate their efficiencies. This permits us to separately identify how locational, proprietary, and organizational characteristics of a firm affect its performance.

Labor-Use Efficiency in Indian Banking: A Branch Level Analysis

This paper uses Data Envelopment Analysis to measure labor use efficiency of individual branches of a large public sector bank with several thousand branches across India. We find considerable variation in the average levels of efficiency across the four metropolitan regions considered in this study. In this context, we introduce the concept of area or spatial efficiency for each region relative to the nation as a whole. Our findings suggest that the policies, procedures, and incentives handed down from the corporate level cannot fully neutralize the influence of the local work culture in the different regions. Most of the potential reduction in labor cost appears to be coming from possible downsizing the clerical and subordinate staff. Our analysis identifies branches that operate at very low levels of efficiency and may be gainfully merged with other branches wherever possible.

Student Performance in Traditional vs. Online Format: Evidence from an MBA Level Introductory Economics Class

All previous studies comparing online and face-to-face format for instruction of economics compared courses that were either online or face-to-face format and regressed exam scores on selected student characteristics. This approach is subject to the econometric problems of self-selection omitted unobserved variables. Our study uses two methods to deal with these problems. First we eliminate self-selection bias by using students from a course that uses both instruction formats. Second, we use the exam questions as the unit of observation, and eliminate omitted variable bias by using an indicator variable for each student to capture the effect of differences in unobserved student characteristics on learning outcomes. We report the finding that students had a significantly greater chance of answering a question correctly if it came from a chapter covered online.

HPV vaccine coverage in Texas counties: An application of multilevel, small area estimation

Health departments, research institutions, policy-makers, and healthcare providers are often interested in knowing the health status of their clients/constituents. Without the resources, financially or administratively, to go out into the community and conduct health assessments directly, these entities frequently rely on data from population-based surveys to supply the information they need. Unfortunately, these surveys are ill-equipped for the job due to sample size and privacy concerns. Small area estimation (SAE) techniques have excellent potential in such circumstances, but have been underutilized in public health due to lack of awareness and confidence in applying its methods. The goal of this research is to make model-based SAE accessible to a broad readership using clear, example-based learning. Specifically, we applied the principles of multilevel, unit-level SAE to describe the geographic distribution of HPV vaccine coverage among females aged 11-26 in Texas.^ Multilevel (3 level: individual, county, public health region) random-intercept logit models of HPV vaccination (receipt of ≥ 1 dose Gardasil® ) were fit to data from the 2008 Behavioral Risk Factor Surveillance System (outcome and level 1 covariates) and a number of secondary sources (group-level covariates). Sampling weights were scaled (level 1) or constructed (levels 2 & 3), and incorporated at every level. Using the regression coefficients (and standard errors) from the final models, I simulated 10,000 datasets for each regression coefficient from the normal distribution and applied them to the logit model to estimate HPV vaccine coverage in each county and respective demographic subgroup. For simplicity, I only provide coverage estimates (and 95% confidence intervals) for counties.^ County-level coverage among females aged 11-17 varied from 6.8-29.0%. For females aged 18-26, coverage varied from 1.9%-23.8%. Aggregated to the state level, these values translate to indirect state estimates of 15.5% and 11.4%, respectively; both of which fall within the confidence intervals for the direct estimates of HPV vaccine coverage in Texas (Females 11-17: 17.7%, 95% CI: 13.6, 21.9; Females 18-26: 12.0%, 95% CI: 6.2, 17.7).^ Small area estimation has great potential for informing policy, program development and evaluation, and the provision of health services. Harnessing the flexibility of multilevel, unit-level SAE to estimate HPV vaccine coverage among females aged 11-26 in Texas counties, I have provided (1) practical guidance on how to conceptualize and conduct modelbased SAE, (2) a robust framework that can be applied to other health outcomes or geographic levels of aggregation, and (3) HPV vaccine coverage data that may inform the development of health education programs, the provision of health services, the planning of additional research studies, and the creation of local health policies.^

THE APPLICATION OF PATH ANALYSIS TO ASSESSMENT OF IRON NUTRITIONAL STATUS IN MAN

Path analysis has been applied to components of the iron metabolic system with the intent of suggesting an integrated procedure for better evaluating iron nutritional status at the community level. The primary variables of interest in this study were (1) iron stores, (2) total iron-binding capacity, (3) serum ferritin, (4) serum iron, (5) transferrin saturation, and (6) hemoglobin concentration. Correlation coefficients for relationships among these variables were obtained from published literature and postulated in a series of models using measures of those variables that are feasible to include in a community nutritional survey. Models were built upon known information about the metabolism of iron and were limited by what had been reported in the literature in terms of correlation coefficients or quantitative relationships. Data were pooled from various studies and correlations of the same bivariate relationships were averaged after z- transformations. Correlation matrices were then constructed by transforming the average values back into correlation coefficients. The results of path analysis in this study indicate that hemoglobin is not a good indicator of early iron deficiency. It does not account for variance in iron stores. On the other hand, 91% of the variance in iron stores is explained by serum ferritin and total iron-binding capacity. In addition, the magnitude of the path coefficient (.78) of the serum ferritin-iron stores relationship signifies that serum ferritin is the most important predictor of iron stores in the proposed model. Finally, drawing upon known relations among variables and the amount of variance explained in path models, it is suggested that the following blood measures should be made in assessing community iron deficiency: (1) serum ferritin, (2) total iron-binding capacity, (3) serum iron, (4) transferrin saturation, and (5) hemoglobin concentration. These measures (with acceptable ranges and cut-off points) could make possible the complete evaluation of all three stages of iron deficiency in those persons surveyed at the community level. ^

APPLICATION OF THE BRAINSTEM EVOKED RESPONSE (BER) TO NEUROTOXICITY EVALUATION OF THE AUDITORY SYSTEM: ASSESSMENT OF INORGANIC LEAD-INDUCED OTOTOXICITY

An experimental procedure was developed using the Brainstem Evoked Response (BER) electrophysiological technique to assess the effect of neurotoxic substances on the auditory system. The procedure utilizes Sprague-Dawley albino rats who have had dural electrodes implanted in their skulls, allowing neuroelectric evoked potentials to be recorded from their brainstems. Latency and amplitude parameters derived from the evoked potentials help assess the neuroanatomical integrity of the auditory pathway in the brainstem. Moreover, since frequency-specific auditory stimuli are used to evoke the neural responses, additional audiometric information is obtainable. An investigation on non-exposed control animals shows the BER threshold curve obtained by tests at various frequencies very closely approximates that obtained by behavioral audibility tests. Thus, the BER appears to be a valid measure of both functional and neuroanatomical integrity of the afferent auditory neural pathway.^ To determine the usefulness of the BER technique in neurobehavioral toxicology research, a known neurotoxic agent, Pb, was studied. Female Sprague-Dawley rats were dosed for 45 days with low levels of Pb acetate in their drinking water, after which BER recordings were obtained. The Pb dosages were determined from the findings of an earlier pilot study. One group of 6 rats received normal tap water, one group of 7 rats received a solution of 0.1% Pb, and another group of 7 rats received a solution of 0.2% Pb. After 45 days, the three groups exhibited blood Pb levels of 4.5 (+OR-) 0.43 (mu)g/100 ml, 37.8 (+OR-) 4.8 (mu)g/100 ml and 47.3 (+OR-) 2.7 (mu)g/100 ml, respectively.^ The results of the BER recording indicated evoked response waveform latency abnormalities in both the Pb-treated groups when midrange frequency (8 kHz to 32 kHz) stimuli were used. For the most part, waveform amplitudes did not vary significantly from control values. BER recordings obtained after a 30-day recovery period indicated the effects seen in the 0.1% Pb group had disappeared. However, those anomalies exhibited by the 0.2% Pb group either remained or increased in number. This outcome indicates a longer lasting or possibly irreversible effect on the auditory system from the higher dose of Pb. The auditory pathway effect appears to be in the periphery, at the level of the cochlea or the auditory (VIII) nerve. The results of this research indicate the BER technique is a valuable and sensitive indicator of low-level toxic effects on the auditory system.^

The Relationship of Provincial Economic Level and Child Injury Mortality in Thailand: A Cross-Sectional Analysis in a Middle Income Country

The objective of this cross-sectional study was to examine the relationship of provincial economic development indices with incidences of child injury mortality in Thailand from 1999 - 2001. All injury deaths among children age 1-14 years were included. The independent variables included gross provincial product per capita (GPP/c), poverty and inequality indices, material and social deprivation indices, population in rural/ urban areas, and migration. Due to multicollinearity of such variables, the 76 provinces were categorized by GPP/c quartile, and means of overall injury, drowning, and transport-related mortality rates were compared among quartile groups. Spearman’s rho correlation between GPP/c and injury mortality rates was also performed. Finally, factor analysis was employed to create a set of factors to be treated as uncorrelated variables and stepwise multiple regression was carried out for the effects of the factors on injury mortality rates. A significant direct relationship was observed between GPP/c and overall injury mortality among children age 1-4 years, and 10-14 year-olds of both genders. Drowning was the main cause of this relationship among children age 1-4 years, and transport-related injury was the principle cause among children age 10-14 years. Conversely, provinces with lower GPP/c experienced higher injury mortality rates among school-age children 5-9 years old for both genders, mostly due to drowning. Factor analysis, and multiple regression results confirmed the relationships between economic development and injury mortality rates. These findings revealed that economic development had an adverse impact on injury-related mortality among children 1 to 4 and 10 to14 in Thailand.