Is the Informal Sector Constrained from the Demand Side? Evidence for Six West African Capitals

Employing a unique dataset that covers households from six West African capitals, this paper provides new evidence on the demand for informal sector products and services. We first investigate whether demand linkages exist between formal and informal products and distribution channels, and whether there is an overlapping customer base, which would imply that both formal sector wage earners and informal workers buy both formal and informal products using both formal and informal distribution channels. In a second step, we estimate demand elasticities based on Engel curves. We find a strongly overlapping customer base and strong demand-side linkages between the formal and informal sector, with the exception that informal goods are hardly bought through formal distribution channels. The estimated demand elasticities tend to show that rising incomes are associated with a lower propensity to consume informal sector goods and to use informal distribution channels. We therefore conclude that the informal sector in West Africa is likely to be constrained from the demand side. --Informal sector,formal-informal linkages,Engel curve estimates,West Africa

Chinas Landesverteidigung am Beginn der 2020er Jahre: Weißbuch zu Chinas Militärstrategie

Thema: Chinas Landesverteidigung am Beginn der 2020er Jahre - im Spiegel des Weißbuchs 2019 zur Militärstrategie Chinas. • mit einem Kommentar. • Chinas Weißbuch 2019, gekürzte und bearb. Übersetzung a. d. Engl.; • Chinas Weißbuch 2019, Textoriginal (engl.); • Chinas Weißbuch 2015, gekürzte und bearb. Übersetzung a. d. Engl.:Inhalt: • Vorwort des Herausgebers • Kommentar von Wilfried Schreiber: 'Chinas Weißbuch 2019 zur Militärstrategie und die KP Chinas.' • Übersetzung von Bernd Biedermann: Weißbuch 2019 zu Chinas Militärstrategie. 'Chinas Landesverteidigung im neuen Zeitalter.' • Anhang 1: Übersetzung von Bernd Biedermann: 'Weißbuch 2015 zu Chinas Militärstrategie.' • Anhang 2: Textoriginal (engl.): White paper 2019 - 'China`s National Defense in the New Era (2019)

Trembling triggers: exploring the sensitivity of backdoors in DNN-based face recognition

Abstract Backdoor attacks against supervised machine learning methods seek to modify the training samples in such a way that, at inference time, the presence of a specific pattern (trigger) in the input data causes misclassifications to a target class chosen by the adversary. Successful backdoor attacks have been presented in particular for face recognition systems based on deep neural networks (DNNs). These attacks were evaluated for identical triggers at training and inference time. However, the vulnerability to backdoor attacks in practice crucially depends on the sensitivity of the backdoored classifier to approximate trigger inputs. To assess this, we study the response of a backdoored DNN for face recognition to trigger signals that have been transformed with typical image processing operators of varying strength. Results for different kinds of geometric and color transformations suggest that in particular geometric misplacements and partial occlusions of the trigger limit the effectiveness of the backdoor attacks considered. Moreover, our analysis reveals that the spatial interaction of the trigger with the subject's face affects the success of the attack. Experiments with physical triggers inserted in live acquisitions validate the observed response of the DNN when triggers are inserted digitally