Minimum variance stratification of a finite population

This paper considers the combined problem of allocation and stratification in order to minimise the variance of the expansion estimator of a total, taking into account that the population is finite. The proof of necessary minimum variance conditions utilises the Kuhn-Tucker Theorem. Stratified simple random sampling with non-negligible sampling fractions is an important design in sample surveys. We go beyond limiting assumptions that have often been used in the past, such as that the stratification equals the study variable or that the sampling fractions are small. We discuss what difference the sampling fractions will make for stratification. In particular, in many surveys the sampling fraction equals one for some strata. The main theorem of this paper is applied to two populations with different characteristics, one of them being a business population and the other one a small population of 284 Swedish municipalities. We study empirically the sensitivity of deviations from the optimal solution

Feeding back Information on Ineligibility from Sample Surveys to the Frame

It is usually discovered in the data collection phase of a survey that some units in the sample are ineligible even if the frame information has indicated otherwise. For example, in many business surveys a nonnegligible proportion of the sampled units will have ceased trading since the latest update of the frame. This information may be fed back to the frame and used in subsequent surveys, thereby making forthcoming samples more efficient by avoiding sampling nonnegligible units. We investigate what effect on survey estimation the process of feeding back information on ineligibility may have, and derive an expression for the bias that can occur as a result of feeding back. The focus is on estimation of the total using the common expansion estimator. We obtain an estimator that is nearly unbiased in the presence of feed back. This estimator relies on consistent estimates of the number of eligible and ineligible units in the population being available

Archival Programs in the Southeast: A Preliminary Assessment

In February of 1981, the National Historical Publications and Records Commission (NHPRC), a small federal funding agency located within the National Archives and Records Service, made a large bet on what Jimmy the Greek would surely have declared to be an archival longshot

Performance Indices: Ranking the Rankings

Performance indices, which rank social issues or policy outcomes in different countries by combining related measures into a single score for each, are enjoying a boom. Their number has soared over the past two decades. They are popular, influential—and sometimes flawed

Can Prostitution Law Reform Curb Sex Trafficking? Theory and Evidence on Scale Substitution, and Replacement Effects

Sex trafficking, a pervasive problem in many parts of the world, has become increasingly salient to policymakers and the general public. Activists, politicians, and scholars continue to engage in debates about how best to curb it. This Article discusses one especially contentious dimension of these debates: does banning prostitution reduce sex trafficking? Or is legalizing prostitution the optimal approach? Or is there a third, better way? Proceeding both theoretically and empirically, this Article seeks to cast light on the relationship between different types of prostitution laws and the prevalence of sex trafficking and human trafficking. It attempts to make three contributions to the literature. First, it builds on existing theories of the link between the demand for purchased sex and the supply of sex-trafficking victims to create a simple ordinal measure of prostitution laws. This measure, which the Article dubs the Prostitution Law Index (PLI), captures not only whether prostitution overall is legal or illegal, but whether buying sex is legal or illegal and whether selling sex is legal or illegal, which better reflects the actual cross-country variation in prostitution laws. The PLI takes into account scale, substitution, and replacement effects in the market for prostitution, where scale refers to increases in the prevalence of trafficking that are caused by growth of the overall market for prostitution; substitution to decreases in trafficking caused by current consumers who purchase sex with trafficking victims and, based on the risk of criminal sanction, shift to instead purchasing sex with individuals who voluntarily sell sex, thereby crowding out trafficking victims; and replacement to decreases in trafficking caused by new voluntary sellers of sex who, incentivized by changes in prostitution laws, enter the market and crowd out trafficking victims. The PLI ranks prostitution laws across countries on a four-point scale (from 1 to 4), based on their expected effectiveness (from least to most effective) in reducing sex trafficking. Second, the study uses a recent dataset provided by the European Union to map the statistical relationship between PLI scores and prevalence of sex trafficking, based on the Article’s theory of scale, substitution, and replacement effects. The analysis suggests that there generally is an inverse relationship between a country’s PLI score and the prevalence of trafficking in that country. Greater legislative efforts to reduce scale and to increase substitution and replacement appear, on average, to be associated with lower levels of sex trafficking. Third, the Article presents a basic Difference-in-Differences analysis—on the basis of extremely limited data and thus with an unusually large number of caveats— of Norway’s 2009 prostitution law reform. Tentative results indicate that the Norwegian reform, which made it legal to sell but illegal to buy sex, may potentially have helped reduce the prevalence of trafficking there

The essentiality of DivIVAEf oligomerization for proper cell division in enterococcus faecalis and interaction with a novel cell division protein

DivIVA is a Gram-positive cell division protein involved in chromosome segregation, midcell placement of the cell division machinery, complete septum closure, and polar growth and morphogenesis. Although well conserved across various Gram-positive species, DivIVA is believed to be relatively species specific. One similarity among DivIVA homologues is the ability to oligomerize through coiled-coil interaction into complexes comprising 10-12 monomers. To date, the importance of DivIVA oligomerization and the N-terminal coiled-coil for its proper function in bacterial cell division has not been reported. This study examined the biological significance of DivIVA oligomerization and the N-terminal coiled-coil in bacterial cell division. This research provides evidence that the N-terminal coiled-coil and oligomerization is essential for the proper biological function of DivIVAEf in Enterococcus faecalis cell division. Introduction of point mutations into chromosomal divIVAEf known to disrupt either the N-terminal coiled-coil or the two central coiled-coils, involved in oligomerization, were found to be lethal unless rescued by in trans expression of wild type DivIVAEf. Using this rescue method, the N-terminal divIVAEf mutant strain, E. faecalis MWMR5, and the mutant strain with partial disruption of oligomerization, E. faecalis MWMR10, were successfully rescued. Differential Interference Contrast (DIC) and Transmission Electron Microscopy (TEM) were utilized to determine the phenotypes of divIVAEf mutant strains E. faecalis MWMR5 and MWMR10. Both these strains showed asymmetrical division, loss of normal lancet shape, and irregular chains. Full disruption of oligomerization with point mutations in both central coiled-coils resulted in a dominant lethal phenotype. These results demonstrate the essentiality of the N-terminal coiled-coil and oligomerization of DivIVAEf for its proper biological function in E. faecalis cell division. Previous detection of DivIVA interaction with a novel cell division protein, MLJD1, by screening a Yeast Two-Hybrid (Y2H) was weak. GST-pulldown and immunoprecipitation did indicate DivIVAEf interaction with MLJD1, but another in vivo assay was required to support these results. In this study I demonstrate a strong interaction, using an in vivo Bacterial Two-Hybrid (B2H) assay, between DivIVAEf and a fragment of MLJD1 containing two cystathionine-beta-synthase (CBS) domains. The in vitro and in vivo results thus confirm interaction between DivIVAEf and MLJD1. Another objective of this study was to determine the localization of DivIVA and MLJD1 in E. faecalis. Localization of DivIVAEf in E. faecalis was found to be similar to DivIVA localization in Bacillus subtilis and Streptococcus pneumonia. DivIVAEf was diffused along the cell membrane and, as chromosome replication and segregation and cell division proceeded, DivIVAEf migrated to the cell poles and then concurrently to the division site. Intriguingly, MLJD1 was found to localize in the same pattern as DivIVAEf in E. faecalis, further implicating MLJD1 as a bacterial cell division protein. Since MLJD1 has potential DNA binding capabilities a proposed model of its role in cell division has been proposed. I hypothesize that MLJD1 could be forming a bridge between DivIVAEf and the chromosome to aid in proper chromosomal replication and segregation. This model could explain how DivIVAEf is involved in chromosome replication. This model is similar to the role of RacA in sporulation in B. subtilis where RacA directs the chromosome during sporulation through direct interaction with DivIVABs and Spo0J. This study has set some important and essential ground work for developing a novel model of cell division for the elusive Gram-positive coccal bacterial strains