A note on measuring group performance over time with pseudo-panels

Aparicio et al. (2017) recently extended the Camanho and Dyson (2006) Malmquist-type index (CDMI) for determining group performance in cross-sectional studies to panel or pseudo-panel databases. In that paper, it was shown that the pseudo-panel Malmquist index (PPMI) can be easily interpreted as the ratio of aggregated productivity changes in two groups of decision making units over time if and only if a new -difficult to interpret- term, the so called ‘divergence component’ (DC), is equal to one. The aim of this paper is twofold. First, based upon considering a baseline group technology we define a new base-group base-period PPMI where the DC always vanished. Second, when more than two groups are analyzed we show that under this framework the new base-group base-period PPMI, the new base-group CDMI and the components of both indexes satisfy the circular relation. As a consequence, the complicated ‘adjusted index’ defined in Camanho and Dyson (2006) for measuring the technology gap to satisfy the circular relation also vanishes. Both results will make it easier for practitioners applying the two indexes in different economic sectors regardless of how many groups are being compared

Herding Vulnerable Cats: A Statistical Approach to Disentangle Joint Responsibility for Web Security in Shared Hosting

Hosting providers play a key role in fighting web compromise, but their ability to prevent abuse is constrained by the security practices of their own customers. {\em Shared} hosting, offers a unique perspective since customers operate under restricted privileges and providers retain more control over configurations. We present the first empirical analysis of the distribution of web security features and software patching practices in shared hosting providers, the influence of providers on these security practices, and their impact on web compromise rates. We construct provider-level features on the global market for shared hosting -- containing 1,259 providers -- by gathering indicators from 442,684 domains. Exploratory factor analysis of 15 indicators identifies four main latent factors that capture security efforts: content security, webmaster security, web infrastructure security and web application security. We confirm, via a fixed-effect regression model, that providers exert significant influence over the latter two factors, which are both related to the software stack in their hosting environment. Finally, by means of GLM regression analysis of these factors on phishing and malware abuse, we show that the four security and software patching factors explain between 10\% and 19\% of the variance in abuse at providers, after controlling for size. For web-application security for instance, we found that when a provider moves from the bottom 10\% to the best-performing 10\%, it would experience 4 times fewer phishing incidents. We show that providers have influence over patch levels--even higher in the stack, where CMSes can run as client-side software--and that this influence is tied to a substantial reduction in abuse levels

Using Pseudo-Panels to Measure Income Mobility in Latin America

This paper presents a comparative overview of mobility patterns in 14 Latin American countries between 1992 and 2003. Using three alternative econometric techniques on constructed pseudo-panels, the paper provides a set of estimators for the traditional notion of income mobility as well as for mobility around extreme and moderate poverty lines. The estimates suggest very high levels of time-dependent unconditional immobility for the Region. However, the introduction of socioeconomic and personal factors reduces the estimate of income immobility by around 30 percent. There are also large variations in country-specific income mobility (estimated to explain some additional 10 percent of inter-temporal income variation). Analyzing the determinants of changes in poverty incidence within cohorts revealed statistically significant roles for age, gender and education of the household head, the latter subject to distinctive effects across levels of attainment and transition in and out of poverty.Latin America, poverty, income mobility, pseudo-panels

Impact of modulation on CMB B-mode polarization experiments

We investigate the impact of both slow and fast polarization modulation strategies on the science return of upcoming ground-based experiments aimed at measuring the B-mode polarization of the CMB. Using simulations of the Clover experiment, we compare the ability of modulated and un-modulated observations to recover the signature of gravitational waves in the polarized CMB sky in the presence of a number of anticipated systematic effects. The general expectations that fast modulation is helpful in mitigating low-frequency detector noise, and that the additional redundancy in the projection of the instrument's polarization sensitivity directions onto the sky when modulating reduces the impact of instrumental polarization, are borne out by our simulations. Neither low-frequency polarized atmospheric fluctuations nor systematic errors in the polarization sensitivity directions are mitigated by modulation. Additionally, we find no significant reduction in the effect of pointing errors by modulation. For a Clover-like experiment, pointing jitter should be negligible but any systematic mis-calibration of the polarization coordinate reference system results in significant E-B mixing on all angular scales and will require careful control. We also stress the importance of combining data from multiple detectors in order to remove the effects of common-mode systematics (such as 1/f atmospheric noise) on the measured polarization signal. Finally we compare the performance of our simulated experiment with the predicted performance from a Fisher analysis. We find good agreement between the Fisher predictions and the simulations except for the very largest scales where the power spectrum estimator we have used introduces additional variance to the B-mode signal recovered from our simulations.Comment: Replaced with version accepted by MNRAS. Analysis of half-wave plate systematic (differential transmittance) adde

Estimating the wage premium to supervision for middle managers in different contexts: evidence from Germany and the UK

The analysis of wage distribution has attracted scholars from different disciplines seeking to develop theoretical arguments to explain the upward or downward trend. In particular, how the middle management wage premium changes in different contexts is a relatively neglected area of research. This study argues that wage distribution changes in different contexts, representing different forms of capitalism. To shed light on this, we considered the size and the shape of the wage premium to supervision paid to middle managers in Germany and the UK. We find evidence of two forms of context: middle managers are paid differently for the same task according to the economy where they work; of this amount, about half of the difference is related to the context. We frame the analysis within the literature on varieties of capitalism

Self-Employment and Risk Preference

We explore the relationship between self-employment and attitudes towards financial risk using individual level data drawn from the U.S. Survey of Consumer Finances (SCF) and the U.S. Panel Study of Income Dynamics (PSID). Both surveys include questions, which enable us to construct measures of an individual´s willingness to take risk allowing us to explore the implications of interpersonal differences in risk preference for the probability and success of self-employment. Our empirical findings suggest that willingness to take financial risk is positively associated with both the incidence and success of self-employment. We find that this relationship is particularly pronounced in cases where the individual actually started the business. Finally, we exploit the panel aspect of the PSID and find evidence consistent with a causal relationship between attitudes towards risk and self-employment with attitudes towards risk measured over 1969-1972 (i.e. prior to becoming self-employed) having a statistically significant positive influence on the probability of self-employment in 1996

Compressive Sensing for Spectroscopy and Polarimetry

We demonstrate through numerical simulations with real data the feasibility of using compressive sensing techniques for the acquisition of spectro-polarimetric data. This allows us to combine the measurement and the compression process into one consistent framework. Signals are recovered thanks to a sparse reconstruction scheme from projections of the signal of interest onto appropriately chosen vectors, typically noise-like vectors. The compressibility properties of spectral lines are analyzed in detail. The results shown in this paper demonstrate that, thanks to the compressibility properties of spectral lines, it is feasible to reconstruct the signals using only a small fraction of the information that is measured nowadays. We investigate in depth the quality of the reconstruction as a function of the amount of data measured and the influence of noise. This change of paradigm also allows us to define new instrumental strategies and to propose modifications to existing instruments in order to take advantage of compressive sensing techniques.Comment: 11 pages, 9 figures, accepted for publication in A&