558 research outputs found
The Tail of Two Countries: Minimum Wages and Employment in France and the United States
We use longitudinal individual wage and employment data in France and the United States to
investigate the effect of changes in the real minimum wage rate on an individual?s employment
status. We focus on workers employed at wages close enough to the minimum in a reference
year as to be illegal in an adjacent comparison year as a result of movements in the real
minimum wage. We find that movements in the American real minimum wage are associated
with no employment effects, whereas movements in the cost of French minimum wage workers
are associated with very strong negative employment effects. Our analysis is based upon
identifying the direct effect of the change in the real minimum wage rate on exits from (entry into)
employment when the real minimum wage rate increases (respectively, decreases) and
identifying the heterogeneity in the behavior of our treatment and control groups using a pseudoexperimental
contrast. We relate the difference-in-difference estimator directly to demand and
supply elasticities for the two groups
Diurnal to interannual variability of low‐level cloud cover over western equatorial Africa in May–October
This study examines the diurnal to interannual variations of the stratiform cloud cover in May–October (1971–2019) from a 3-hourly station database and from ERA5 reanalyses over western equatorial Africa (WEA). The main diurnal variations of the local-scale fraction and genus of stratiform clouds are synthesized into three canonical diurnal types (i.e., “clear,” “clear afternoon,” “cloudy” days). The interannual variations of frequencies of the three diurnal types during the cloudiest months (JJAS) are mostly associated with two main mechanisms: a meridional shallow overturning cell associating more “cloudy” and less “clear” and “clear afternoon” days to anomalous southerlies below 900 hPa over and around WEA, anomalous ascent around 5°–7°N, anomalous northerlies between 875 and 700 hPa, and anomalous subsidence over the equatorial Atlantic. This circulation is strongly related to interannual variations of the equatorial Atlantic upwelling (i.e., more clouds when the upwelling is strong) associated with a meridional shift of the Intertropical Convergence Zone over the Tropical Atlantic and adjacent continents. The second mechanism operates mostly in the zonal direction and involves again the coupled ocean–atmosphere system over the equatorial Atlantic, but also the remote El Niño–Southern Oscillation (ENSO). An anomalously cold equatorial Atlantic drives increased low-level westerlies toward the Congo Basin. Warm ENSO events promote broad warm and easterly anomalies in the middle and upper troposphere, which increase the local static stability, and thus the local stratiform cloud cover over WEA. The present study suggests new mechanisms responsible for interannual variations of stratiform clouds in WEA, thus providing avenues of future research regarding the stability of the stratiform cloud deck under the ongoing differential warming of tropical ocean and land masses
The incidence of total hip arthroplasty after hip arthroscopy in osteoarthritic patients
<p>Abstract</p> <p>Objective</p> <p>To assess the incidence of total hip arthroplasty (THA) in osteoarthritic patients who were treated by arthroscopic debridement and to evaluate factors that might influence the time interval from the first hip arthroscopy to THA.</p> <p>Design</p> <p>Retrospective clinical series</p> <p>Methods</p> <p>Follow-up data and surgical reports were retrieved from 564 records of osteoarthritic patients that have had hip arthroscopy between the years 2002 to 2009 with a mean follow-up time of 3.2 years (range, 1-6.4 years). The time interval between the first hip arthroscopy to THA was modelled as a function of patient age; level of cartilage damage; procedures performed and repeated arthroscopies with the use of multivariate regression analysis.</p> <p>Results</p> <p>Ninety (16%) of all participants eventually required THA. The awaiting time from the first arthroscopy to a hip replacement was found to be longer in patients younger than 55 years and in a milder osteoarthritic stage. Patients that experienced repeated hip scopes had a longer time to THA than those with only a single procedure. Procedures performed concomitant with debridement and lavage did not affect the time interval to THA.</p> <p>Conclusions</p> <p>In our series of arthroscopic treatment of hip osteoarthritis, 16% required THA over a period of 7 years. Factors that influence the time to arthroplasty were age, degree of osteoarthritis and recurrent procedures.</p
Security analyst networks, performance and career outcomes
Authors' draft. Final version to be published in The Journal of Finance. Available online at http://onlinelibrary.wiley.com/Using a sample of 42,376 board directors and 10,508 security analysts we construct a social
network, mapping the connections between analysts and directors, between directors, and
between analysts. We use social capital theory and techniques developed in social network
analysis to measure the analyst’s level of connectedness and investigate whether these
connections provide any information advantage to the analyst. We find that better-connected
(better-networked) analysts make more accurate, timely, and bold forecasts. Moreover, analysts
with better network positions are less likely to lose their job, suggesting that these analysts are
more valuable to their brokerage houses. We do not find evidence that analyst innate forecasting
ability predicts an analyst’s future network position. In contrast, past forecast optimism has a
positive association with building a better network of connections
Elliptic logarithms, diophantine approximation and the Birch and Swinnerton-Dyer conjecture
Most, if not all, unconditional results towards the abc-conjecture rely
ultimately on classical Baker's method. In this article, we turn our attention
to its elliptic analogue. Using the elliptic Baker's method, we have recently
obtained a new upper bound for the height of the S-integral points on an
elliptic curve. This bound depends on some parameters related to the
Mordell-Weil group of the curve. We deduce here a bound relying on the
conjecture of Birch and Swinnerton-Dyer, involving classical, more manageable
quantities. We then study which abc-type inequality over number fields could be
derived from this elliptic approach.Comment: 20 pages. Some changes, the most important being on Conjecture 3.2,
three references added ([Mas75], [MB90] and [Yu94]) and one reference updated
[BS12]. Accepted in Bull. Brazil. Mat. So
WARNING: Physics Envy May Be Hazardous To Your Wealth!
The quantitative aspirations of economists and financial analysts have for
many years been based on the belief that it should be possible to build models
of economic systems - and financial markets in particular - that are as
predictive as those in physics. While this perspective has led to a number of
important breakthroughs in economics, "physics envy" has also created a false
sense of mathematical precision in some cases. We speculate on the origins of
physics envy, and then describe an alternate perspective of economic behavior
based on a new taxonomy of uncertainty. We illustrate the relevance of this
taxonomy with two concrete examples: the classical harmonic oscillator with
some new twists that make physics look more like economics, and a quantitative
equity market-neutral strategy. We conclude by offering a new interpretation of
tail events, proposing an "uncertainty checklist" with which our taxonomy can
be implemented, and considering the role that quants played in the current
financial crisis.Comment: v3 adds 2 reference
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