7,699 research outputs found
Agricultural Research and Poverty Alleviation: Some International Perspectives
Invited paper for the John L. Dillon AO Commemorative Day on ‘Agricultural Research: Challenges and Economics in the New Millenium’ The University of New England, Armidale NSW Australia, September 20, 2002Food Security and Poverty, Research and Development/Tech Change/Emerging Technologies,
Synthesis report of workshop on assessing the impact of policy-oriented social science research in Scheveningen, The Netherlands, November 12-13 2001
Economists have engaged for some time in developing methodologies for assessing the economic impact of agricultural research and in undertaking empirical studies to measure this impact. In recent years, they have documented more than 1,800 estimates of rates of return to agricultural research. Economists have paid little attention, however, to how to evaluate the impact of social science research. A symposium conducted by IFPRI in 1997 was one of the first attempts to address this knowledge gap. In November 2001, the Netherlands Ministry of Foreign Affairs and IFPRI brought together a group of researchers to follow up on the earlier symposium. Their conclusions fell into two broad categories: how to measure or value the economic impact of policy-oriented social science research and how to enhance the effectiveness of such research in policymaking environments. A number of lessons emerged from the workshop for donors, governments, and researchers about how to enhance the effectiveness of policy-oriented social science research....Because much remains to be learned about evaluating the impact of policy-oriented social science research, the workshop participants concluded that IFPRI should take the lead in developing a consortium to help improve interdisciplinary methods of assessing impact. The consortium would consist of institutions, donors, and individuals and would work in partnership with developing countries. Institutions could learn from each other about best practices and in the process exploit synergies, thereby increasing effectiveness and reducing the costs of what is an expensive undertaking.Agricultural research Economic aspects. ,Evaluation. ,Rate of return. ,Social sciences Research Evaluation. ,Research Economic aspects Congresses. ,
A Perspective on Unique Information: Directionality, Intuitions, and Secret Key Agreement
Recently, the partial information decomposition emerged as a promising
framework for identifying the meaningful components of the information
contained in a joint distribution. Its adoption and practical application,
however, have been stymied by the lack of a generally-accepted method of
quantifying its components. Here, we briefly discuss the bivariate (two-source)
partial information decomposition and two implicitly directional
interpretations used to intuitively motivate alternative component definitions.
Drawing parallels with secret key agreement rates from information-theoretic
cryptography, we demonstrate that these intuitions are mutually incompatible
and suggest that this underlies the persistence of competing definitions and
interpretations. Having highlighted this hitherto unacknowledged issue, we
outline several possible solutions.Comment: 5 pages, 3 tables;
http://csc.ucdavis.edu/~cmg/compmech/pubs/pid_intuition.ht
Unique Information via Dependency Constraints
The partial information decomposition (PID) is perhaps the leading proposal
for resolving information shared between a set of sources and a target into
redundant, synergistic, and unique constituents. Unfortunately, the PID
framework has been hindered by a lack of a generally agreed-upon, multivariate
method of quantifying the constituents. Here, we take a step toward rectifying
this by developing a decomposition based on a new method that quantifies unique
information. We first develop a broadly applicable method---the dependency
decomposition---that delineates how statistical dependencies influence the
structure of a joint distribution. The dependency decomposition then allows us
to define a measure of the information about a target that can be uniquely
attributed to a particular source as the least amount which the source-target
statistical dependency can influence the information shared between the sources
and the target. The result is the first measure that satisfies the core axioms
of the PID framework while not satisfying the Blackwell relation, which depends
on a particular interpretation of how the variables are related. This makes a
key step forward to a practical PID.Comment: 15 pages, 7 figures, 2 tables, 3 appendices;
http://csc.ucdavis.edu/~cmg/compmech/pubs/idep.ht
Unique Information and Secret Key Agreement
The partial information decomposition (PID) is a promising framework for
decomposing a joint random variable into the amount of influence each source
variable Xi has on a target variable Y, relative to the other sources. For two
sources, influence breaks down into the information that both X0 and X1
redundantly share with Y, what X0 uniquely shares with Y, what X1 uniquely
shares with Y, and finally what X0 and X1 synergistically share with Y.
Unfortunately, considerable disagreement has arisen as to how these four
components should be quantified. Drawing from cryptography, we consider the
secret key agreement rate as an operational method of quantifying unique
informations. Secret key agreement rate comes in several forms, depending upon
which parties are permitted to communicate. We demonstrate that three of these
four forms are inconsistent with the PID. The remaining form implies certain
interpretations as to the PID's meaning---interpretations not present in PID's
definition but that, we argue, need to be explicit. These reveal an
inconsistency between third-order connected information, two-way secret key
agreement rate, and synergy. Similar difficulties arise with a popular PID
measure in light the results here as well as from a maximum entropy viewpoint.
We close by reviewing the challenges facing the PID.Comment: 9 pages, 3 figures, 4 tables;
http://csc.ucdavis.edu/~cmg/compmech/pubs/pid_skar.htm. arXiv admin note:
text overlap with arXiv:1808.0860
Modes of Information Flow
Information flow between components of a system takes many forms and is key
to understanding the organization and functioning of large-scale, complex
systems. We demonstrate three modalities of information flow from time series X
to time series Y. Intrinsic information flow exists when the past of X is
individually predictive of the present of Y, independent of Y's past; this is
most commonly considered information flow. Shared information flow exists when
X's past is predictive of Y's present in the same manner as Y's past; this
occurs due to synchronization or common driving, for example. Finally,
synergistic information flow occurs when neither X's nor Y's pasts are
predictive of Y's present on their own, but taken together they are. The two
most broadly-employed information-theoretic methods of quantifying information
flow---time-delayed mutual information and transfer entropy---are both
sensitive to a pair of these modalities: time-delayed mutual information to
both intrinsic and shared flow, and transfer entropy to both intrinsic and
synergistic flow. To quantify each mode individually we introduce our
cryptographic flow ansatz, positing that intrinsic flow is synonymous with
secret key agreement between X and Y. Based on this, we employ an
easily-computed secret-key-agreement bound---intrinsic mutual
information&mdashto quantify the three flow modalities in a variety of systems
including asymmetric flows and financial markets.Comment: 11 pages; 10 figures;
http://csc.ucdavis.edu/~cmg/compmech/pubs/ite.ht
Limits on violations of Lorentz Symmetry from Gravity Probe B
Generic violations of Lorentz symmetry can be described by an effective field
theory framework that contains both general relativity and the standard model
of particle physics called the Standard-Model Extension (SME). We obtain new
constraints on the gravitational sector of the SME using recently published
final results from Gravity Probe B. These include for the first time an upper
limit at the 10^(-3) level on the time-time component of the new tensor field
responsible for inducing local Lorentz violation in the theory, and an
independent limit at the 10^(-7) level on a combination of components of this
tensor field.Comment: 8 pages, 1 figur
- …