Saving, Microinsurance: Why You Should Do Both or Nothing. A Behavioral Experiment on the Philippines

This paper analyzes data from a novel field experiment designed to test the impact of two different insurance products and a secret saving device on solidarity in risk-sharing groups among rural villagers in the Philippines. Risk is simulated by a lottery, risk-sharing is possible in solidarity groups of three and insurance is introduced via less risky lotteries. Our main hypothesis is that formal market-based products lead to lower transfers among network members. We also test for the persistence of this crowding-out of solidarity. We find evidence for a reduction of solidarity by insurance if shocks are observable. Depending on insurance design, there is also evidence for persistence of this effect even if insurance is removed. Simulations using our regression results show that the benefits of insurance are completely offset by the reduction in transfers. However, if secret saving is possible solidarity is very low in general and there is no crowding out effect of insurance. This suggests that introducing formal insurance is not as effective as it is hoped for when the monetary situation can be closely monitored, but that it might be a very important complement when savings inhibit observing financial resources. --

Can microinsurance help prevent child labor? An impact evaluation from Pakistan

Child labor is a common consequence of economic shocks in developing countries. We show how reducing vulnerability can affect child labor and schooling. We exploit the extension of a health and accident insurance scheme by a Pakistani microfinance institution (MFI) that was set up as a randomized controlled trial and accompanied by household panel surveys. Together with increased coverage the MFI offered assistance with claim procedures in treatment branches. Using Difference-in-difference techniques we find lower incidence of child labor and lower child labor earnings caused by the innovation. Separating the two parts of the innovation package, the effects of claim assistance are mostly insignificant, while increased insurance coverage has large effects on child labor outcomes and days missed at school. Consistent with a theoretical model we develop in this paper, the effect is largely due to an ex-ante feeling of protection as opposed to a shock-mitigation effect

Saving, Microinsurance: Why You Should Do Both or Nothing. A Behavioral Experiment on the Philippines

This paper analyzes data from a novel field experiment designed to test the impact of two different insurance products and a secret saving device on solidarity in risk-sharing groups among rural villagers in the Philippines. Risk is simulated by a lottery, risk-sharing is possible in solidarity groups of three and insurance is introduced via less risky lotteries. Our main hypothesis is that formal market-based products lead to lower transfers among network members. We also test for the persistence of this crowding-out of solidarity. We find evidence for a reduction of solidarity by insurance if shocks are observable. Depending on insurance design, there is also evidence for persistence of this effect even if insurance is removed. Simulations using our regression results show that the benefits of insurance are completely offset by the reduction in transfers. However, if secret saving is possible solidarity is very low in general and there is no crowding out effect of insurance. This suggests that introducing formal insurance is not as effective as it is hoped for when the monetary situation can be closely monitored, but that it might be a very important complement when savings inhibit observing financial resources

Limitations of experimental channel characterisation

KURZFASSUNG In dieser Dissertation wird die Experimentelle Kanalcharakterisierung und deren Grenzen in realenAusbreitungsumgebungen untersucht. Dies beinhaltet die Aufzeichnung der mehrdimensionalenbreitbandigen Kanalmatrix mit einem Multiple-Input Multiple-Output (MIMO) Channel-Sounderunter Verwendung von Antennenarrays auf der Sende- und Empfangsseite. Um den Funkkanalmit Hilfe der Parameter Sendewinkel (DoD), Empfangswinkel (DoA), Laufzeit (TDoA) und denkomplexen polarimetrischen Pfadgewichten zu charakterisieren, werden hochauflösende Parameterschätzverfahrenverwendet. Die Genauigkeit dieser Parameterschätzergebnisse in ”realen“ Messumgebungenwird durch eine Vielzahl von Fehlerquellen begrenzt. Diese Genauigkeitsgrenzen derParameterschätzung werden anhand zahlreicher Simulationen und Messungen analysiert. Fehlerquellenim gesamten Verarbeitungsablauf werden untersucht. Dazu gehören die Einschränkungendurch das Messsystem, systematische Fehler bei der Kalibrierung praktischer Antennenarrays sowieUnzulänglichkeiten des Funkkanalmodells des hochauflösenden Parameterschätzers. Darüber hinauswerden die Auswirkungen der Parametrierung bzw. Ableitung geometrisch basierter Kanalmodelleauf der Grundlage von Parameterschätzergebnissen mit begrenzter Genauigkeit aufgezeigt.Mit Messungen in typischen Ausbreitungsumgebungen kann der Funkkanal immer nur in Abhängigkeitder Messantennen beschrieben werden. Als Ziel wird jedoch eine antennenunabhängige Beschreibungdes Funkkanals angestrebt. Daher ist es notwendig, die Sende- und Empfangswinkel derspekularen Ausbreitungspfade mittels hochauflösender Parameterschätzverfahren zu bestimmen.Der gradientenbasierte Maximum Likelihood (ML) Parameterschätzer RIMAX, auf dem diese Arbeitaufbaut, verwendet ein Datenmodell, das den Funkkanal und das Messsystem inklusive derAntennenarrays beschreibt. Im Gegensatz zu anderen ML-Parameterschätzern wird ein Funkanalmodellangewendet, welches spekulare Reflektionen und verteilte diffuse Streuungen berücksichtigt.Für die Modellierung des Messsystems wird ein effizientes und exaktes Modell der gemessenenpolarimetrischen Richtcharakteristika benötigt. Das hier vorgeschlagene Modell, die so genannteEffective Aperture Distribution Function (EADF), beschreibt die Antennenrichtcharakteristikaanalytisch und basiert im Wesentlichen auf der zweidimensionalen (2D) Fouriertransformation derperiodischen Richtcharakteristika. Im Gegensatz zu anderen Verfahren können auf der Grundlageder EADF die Antennencharakteristika und ihre Ableitungen mit geringem Aufwand und hoherGenauigkeit berechnet werden. Für eine exakte Messung der Richtcharakteristika eines Antennenarrayswird ein vollpolarimetrisches 2D-Kalibrierverfahren vorgeschlagen. Mit diesem Verfahrenwird der komplette Messaufbau kalibriert. Dazu gehören der MIMO Channel-Sounder, die dualpolarisierte Referenzhornantenne und alle Hochfrequenzkomponenten außer dem zu untersuchendenAntennenarray. Im Zusammenhang mit der Arraykalibrierung wird ein gradientenbasierterML-Parameterschätzer entwickelt, mit dem eine bei der Kalibriermessung auftretende Phasenabweichungkorrigiert wird. DesWeiteren wird ein leistungsstarkes Verfahren zur Bewertung praktischer Antennenarrays auf derBasis der EADFs gemessener Richtcharakteristika vorgeschlagen. Die Cram´er-Rao-Schranken derWinkelparameter in Abhängigkeit des Signal-Rausch-Verhältnisses werden mit dem EADF-Modellanalytisch berechnet. Der Vorteil des EADF-Modells besteht darin, dass die Richtcharakteristikaeines realen Antennenarrays unter Einbeziehung aller störenden Einflussgrößen beschrieben werden.Das vorgeschlagene Bewertungsverfahren wird anhand von Messungen im Antennenmessraum verifiziert.Das Modell des Messsystems inklusive der Antennenarrays, welches für die Parameterschätzungverwendet wird, kann das reale System nur begrenzt beschreiben. Es wurden Schätzergebnisse vonzahlreichen Messungen analysiert. Hierbei musste festgestellt werden, dass Fehler bei der Modellierungzu teilweise unglaubwürdigen Schätzergebnissen führen. Genauer untersucht werden Fehlerin Bezug auf die Antennenarrays und das Messsystem. Erstere werden hervorgerufen durchsystematische Fehler bei der Arraykalibrierung und durch die Verwendung unvollständiger Datenmodelle(z.B. Nichtberücksichtigung der polarimetrischen Eigenschaften der Antennen). Letztereentstehen einerseits durch Phasenrauschen und andererseits durch ungeeignete Kalibrierung. Eswird nachgewiesen, dass die Verwendung ungenauer Modelle zur Schätzung von Artefakten führt.Diese Schätzfehler äußern sich in Abweichungen und/oder in einer künstlichen Aufspreizung derWinkelschätzungen der spekularen Anteile. Es werden geeignete Methoden vorgeschlagen, um dieAuswirkungen von Modellfehlern weitestgehend zu vermeiden bzw. zu korrigieren. Betont werdenmuss jedoch, dass einige Fehler unvermeidbar sind. Die Auswirkungen aller unvermeidbaren Fehler auf die Experimentelle Kanalcharakterisierung inkomplexen Ausbreitungsumgebungen werden im letzten Teil dieser Arbeit dargestellt. Es wird gezeigt,unter welchen Bedingungen die geschätzten spekularen Anteile sowie die geschätzten verteiltendiffusen Streuanteile glaubwürdig und physikalisch relevant sind. Die Untersuchungen basierenauf ”realistischen“ Simulationen des Funkkanals (Ray-Tracing) und auf Messungen. Diese Synthesegarantiert Glaubwürdigkeit und Aussagefähigkeit der in der Arbeit gewonnenen Ergebnisse.Die Resultate dieser Dissertation sind speziell für Wissenschaftler auf dem Gebiet der Parameterschätzungsowie Funkkanalmodellierung von Interesse und können wie folgt zusammengefasstwerden: • die Entwicklung eines Modells zur exakten und effizienten Beschreibung der Richtcharakteristikavon Antennenarrays,• ein Verfahren zur Bewertung praktischer Antennenarrays,• die Sensibilisierung für Modellfehler und deren Auswirkungen auf die Parameterschätzergebnisseund• die Bestimmung der Grenzen Experimenteller Kanalcharakterisierung unter Berücksichtigungaller unvermeidbarer Fehlerquellen

Building Trust in Rural Producer Organizations in Senegal: Results from a Randomized Controlled Trial

Trust is crucial for successful collective action. A prime example is collective commercialization of agricultural produce through producer organizations. We conduct a cluster-randomized controlled trial in rural Senegal in which we vary the number and the type of smallholder farmers members and/or leaders of local producer organizations invited to a three-day training on collective commercialization. We use this variation to identify effects on intra-group trust, both direct treatment effects of having participated in the training and spillover effects on farmers who did not partake. Looking at different measures of trust in leaders' competence and motives and of trust in members we find that participating in the training significantly enhances both trust in leaders and trust in members. For trust in leaders, we also find a strong spillover effect. Our findings suggest that relatively soft and non-costly interventions such as a group training appear to be able to positively affect trust within producer organizations

Polarization behavior of discrete multipath and diffuse scattering in urban environments at 4.5 GHz

The polarization behavior of the mobile MIMO radio channel is analyzed from polarimetric double-directional channel measurements, which were performed in a macrocell rural environment in Tokyo. The recorded data comprise non-line-of-sight, obstructed line-of-sight, and line-of-sight conditions. The gradient-based maximum-likelihood estimation framework RIMAX was used to estimate both specular and dense multipath components. Joint angular-delay results are gained only for the specular components. The dense multipath components, which may be attributed to diffuse scattering, can be characterized only in delay domain. Different characteristics describing the polarization behavior and power-weighted cross- and copolarization ratios for both types of components are introduced. Statistical analysis of long measurement track segments indicates global trends, whereas local analysis emphasizes specific behavior such as polarization dependency on angle of incidence in streets and under shadowing conditions. The results also underline the importance of modeling changing and transient propagation scenarios which are currently not common in available MIMO channel models

Multi-band propagation and radio channel characterization in street canyon scenarios for 5G and beyond

Radio access at mm-waves has been subject of intensive research in the latest years. However, within the initial deployment of 5G, mm-waves are still relegated and there is a generalized idea that the mm-wave channel for radio access, in comparison to the sub-6 GHz channel, is not only sparse but also troublesome for outdoor applications. In the present paper we introduce simultaneous multi-band measurements comparing the sub-6 GHz with the mm-waves channel at 30 GHz and 60 GHz in street canyon scenarios using the same measurement equipment in Germany and Japan. An analysis on the propagation and radio channel characteristics shows that the mm-waves channel offers similar opportunities as the sub-6 GHz. Consequently, the challenge relies on the design of an adequate radio interface matching the channel characteristics. In that regard, aspects as the location of clusters and spatial consistency gain importance within geometry-based stochastic channel models (GBSCMs). The analysis of the large-scale parameters (LSPs) has shown a large influence of the geometry of the scenario on the channel, encouraging the introduction of deterministic modelling components within GBSCMs targeting these scenarios

Building trust in rural producer organizations: results from a randomized controlled trial

Trust is considered an important factor for successful collective action in groups of smallholder farmers. A prime example is collective commercialization of agricultural produce through producer organizations. While previous research has focused on trust as an exogenous determinant of participation in groups, this article tests whether trust within existing groups can be improved using a training program. We conduct a cluster-randomized controlled trial in rural Senegal to identify the effects of training members and/or leaders with respect to commercialization on intragroup trust. Our design allows identifying both direct treatment effects of having participated in the training and spillover effects on farmers who did not partake. Looking at different measures of trust in leaders’ competence and motives and of trust in members, we find that participating in the training significantly enhances both trust in leaders and trust in members. For trust in leaders, we also find a strong spillover effect. Our findings suggest that relatively soft and noncostly interventions such as group training appear to positively affect trust within producer organizations

Epitope-engineered human hematopoietic stem cells are shielded from CD123-targeted immunotherapy

Targeted eradication of transformed or otherwise dysregulated cells using monoclonal antibodies (mAb), antibody-drug conjugates (ADC), T cell engagers (TCE), or chimeric antigen receptor (CAR) cells is very effective for hematologic diseases. Unlike the breakthrough progress achieved for B cell malignancies, there is a pressing need to find suitable antigens for myeloid malignancies. CD123, the interleukin-3 (IL-3) receptor alpha-chain, is highly expressed in various hematological malignancies, including acute myeloid leukemia (AML). However, shared CD123 expression on healthy hematopoietic stem and progenitor cells (HSPCs) bears the risk for myelotoxicity. We demonstrate that epitope-engineered HSPCs were shielded from CD123-targeted immunotherapy but remained functional, while CD123-deficient HSPCs displayed a competitive disadvantage. Transplantation of genome-edited HSPCs could enable tumor-selective targeted immunotherapy while rebuilding a fully functional hematopoietic system. We envision that this approach is broadly applicable to other targets and cells, could render hitherto undruggable targets accessible to immunotherapy, and will allow continued posttransplant therapy, for instance, to treat minimal residual disease (MRD)