19,459 research outputs found
Reporting biases and survey results: evidence from European professional forecasters
Using data from the ECB's Survey of Professional Forecasters, we investigate the reporting practices of survey participants by comparing their point predictions and the mean/median/mode of their probability forecasts. We find that the individual point predictions, on average, tend to be biased towards favourable outcomes: they suggest too high growth and too low inflation rates. Most importantly, for each survey round, the aggregate survey results based on the average of the individual point predictions are also biased. These findings cast doubt on combined survey measures that average individual point predictions. Survey results based on probability forecasts are more reliable. JEL Classification: C42, E27, E47point estimates, subjective probability distributions, survey methods, Survey of Professional Forecasters (SPF)
Deformation Quantization: Twenty Years After
We first review the historical developments, both in physics and in
mathematics, that preceded (and in some sense provided the background of)
deformation quantization. Then we describe the birth of the latter theory and
its evolution in the past twenty years, insisting on the main conceptual
developments and keeping here as much as possible on the physical side. For the
physical part the accent is put on its relations to, and relevance for,
"conventional" physics. For the mathematical part we concentrate on the
questions of existence and equivalence, including most recent developments for
general Poisson manifolds; we touch also noncommutative geometry and index
theorems, and relations with group theory, including quantum groups. An
extensive (though very incomplete) bibliography is appended and includes
background mathematical literature.Comment: 39 pages; to be published with AIP Press in Proceedings of the 1998
Lodz conference "Particles, Fields and Gravitation". LaTeX (compatibility
mode) with aipproc styl
On the origins of scaling corrections in ballistic growth models
We study the ballistic deposition and the grain deposition models on
two-dimensional substrates. Using the Kardar-Parisi-Zhang (KPZ) ansatz for
height fluctuations, we show that the main contribution to the intrinsic width,
which causes strong corrections to the scaling, comes from the fluctuations in
the height increments along deposition events. Accounting for this correction
in the scaling analysis, we obtained scaling exponents in excellent agreement
with the KPZ class. We also propose a method to suppress these corrections,
which consists in divide the surface in bins of size and use only
the maximal height inside each bin to do the statistics. Again, scaling
exponents in remarkable agreement with the KPZ class were found. The binning
method allowed the accurate determination of the height distributions of the
ballistic models in both growth and steady state regimes, providing the
universal underlying fluctuations foreseen for KPZ class in 2+1 dimensions. Our
results provide complete and conclusive evidences that the ballistic model
belongs to the KPZ universality class in dimensions. Potential
applications of the methods developed here, in both numerics and experiments,
are discussed.Comment: 8 pages, 7 figure
On The Equivalence Of The Mean Variance Criterion And Stochastic Dominance Criteria
We study the necessary and sufficient conditions under which the
Mean-Variance Criterion (MVC) is equivalent to the Maximum Expected Utility
Criterion (MEUC), for two lotteries. Based on Chamberlain (1983), we conclude
that the MVC is equivalent to the Second-order Stochastic Dominance Rule (SSDR)
under any symmetric Elliptical distribution. We then discuss the work of
Schuhmacher et al. (2021). Although their theoretical findings deduce that the
Mean-Variance Analysis remains valid under Skew-Elliptical distributions, we
argue that this does not entail that the MVC coincides with the SSDR. In fact,
generating multiple MV-pairs that follow a Skew-Normal distribution it becomes
evident that the MVC fails to coincide with the SSDR for some types of
risk-averse investors. In the second part of this work, we examine the premise
of Levy and Markowitz (1979) that "the MVC deduces the maximization of the
expected utility of an investor, under any approximately quadratic utility
function, without making any further assumption on the distribution of the
lotteries". Using Monte Carlo Simulations, we find out that the set of
approximately quadratic utility functions is too narrow. Specifically, our
simulations indicate that and are almost quadratic,
while and fail to approximate a quadratic utility
function under either an Extreme Value or a Stable Pareto distribution
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