This paper studies the effects of the apprenticeship system on innovation and labor market polarization. A stylized model with two key features is developed: (1) apprentices are more productive due to industry-specific training, but (2) from the firm’s perspective, when training apprentices, technological innovation is costly since training becomes obsolete. Thus, apprentices correlate with slower adoption of skill-replacing technologies, but also less employment polarization. We test this hypothesis on German regions given local variation in apprenticeship systems until 1976. The results shows no employment polarization related to apprentices, but similar displacement of non-apprentices as in the US.
A recent wave of economic research has studied the transformation of China from a poor country in the 1970s to a middle-income economy today. Based on this literature, we discuss the factors driving China’s development process. We provide a historical account of China’s rise, fall, and resurgence. We then discuss the stylized facts associated with China’s growth process and review a comprehensive theory of its economic transition. Finally, we discuss China’s future. In particular, we review some recent studies about technological and politico-economic factors that may foster or hinder its future economic performance.
Organisms make two types of decisions on a regular basis. Perceptual decisions are determined by objective states of the world (e.g., melons are bigger than apples), whereas value-based decisions are determined by subjective preferences (e.g., I prefer apples to melons). Theoretical accounts suggest that both types of choice involve neural computations accumulating evidence for the choice alternatives; however, little is known about the overlap or differences in the processes underlying perceptual versus value-based decisions. We analyzed EEG recordings during a paradigm where perceptual- and value-based choices were based on identical stimuli. For both types of choice, evidence accumulation was evident in parietal gamma-frequency oscillations, whereas a similar frontal signal was unique for value-based decisions. Fronto-parietal synchronization of these signals predicted value-based choice accuracy. These findings uncover how decisions emerge from topographic- and frequency-specific oscillations that accumulate distinct aspects of evidence, with large-scale synchronization as a mechanism integrating these spatially distributed signals.
We introduce matched-filter fMRI, which improves BOLD (blood oxygen level dependent) sensitivity by variable-density image acquisition tailored to subsequent image smoothing. Image smoothing is an established post-processing technique used in the vast majority of fMRI studies. Here we show that the signal-to-noise ratio of the resulting smoothed data can be substantially increased by acquisition weighting with a weighting function that matches the k-space filter imposed by the smoothing operation. We derive the theoretical SNR advantage of this strategy and propose a practical implementation of 2D echo-planar acquisition matched to common Gaussian smoothing. To reliably perform the involved variable-speed trajectories, concurrent magnetic field monitoring with NMR probes is used. Using this technique, phantom and in vivo measurements confirm reliable SNR improvement in the order of 30% in a "resting-state" condition and prove robust in different regimes of physiological noise. Furthermore, a preliminary task-based visual fMRI experiment equally suggests a consistent BOLD sensitivity increase in terms of statistical sensitivity (average t-value increase of about 35%). In summary, our study suggests that matched-filter acquisition is an effective means of improving BOLD SNR in studies that rely on image smoothing at the post-processing level.
Pre-operative tractography of the optic radiation (OR) has been advised to assess the risk for postoperative visual field deficit (VFD) in certain candidates for resective epilepsy surgery. Diffusion tensor imaging (DTI) tractography relies on a precise anatomical determination of start and target regions of interest (ROIs), such as the lateral geniculate nucleus (LGN) and the primary visual cortex (V1). The post-chiasmal visual pathway and V1 show considerable inter-individual variability, and in epilepsy patients parenchymatous lesions might further complicate this matter. A functionally based tractography (FBT) seems beneficial for precise OR identification. We assessed practicability of FBT for OR identification in a patient with occipital lobe epilepsy due to a temporo-occipital maldevelopmental tumor. The MRI protocol at 3 T included a T1-weighted sagittal 3D scan, a T2-weighted axial 2D scan and a DTI scan using an echo planar spin echo sequence. ROIs for fiber tracking of OR (LGN & V1) were determined with T2*-weighted fMRI-based retinotopic assessment. After DTI pre-processing and fiber tracking, paths with similar properties were combined in clusters for visual presentation and OR localization. Retinotopic phase maps allowed for the identification of V1 and LGN for a precise DTI-based reconstruction of OR, which was distant to the patient's tumor. Location and structure of ORs were comparable in each hemisphere. FBT could thus influence the human research of the extrastriate visual pathway and the risk management of post-operative VFD in epilepsy surgery.
Background: Graph-based analysis of fMRI data has recently emerged as a promising approach to study brain networks. Based on the assessment of synchronous fMRI activity at separate brain sites, functional connectivity graphs are constructed and analyzed using graph-theoretical concepts. Most previous studies investigated region-level graphs, which are computationally inexpensive, but bring along the problem of choosing sensible regions and involve blurring of more detailed information. In contrast, voxel-level graphs provide the finest granularity attainable from the data, enabling analyses at superior spatial resolution. They are, however, associated with considerable computational demands, which can render high-resolution analyses infeasible. In response, many existing studies investigating functional connectivity at the voxel-level reduced the computational burden by sacrificing spatial resolution. Methods: Here, a novel, time-efficient method for graph construction is presented that retains the original spatial resolution. Performance gains are instead achieved through data reduction in the temporal domain based on dichotomization of voxel time series combined with tetrachoric correlation estimation and efficient implementation. Results: By comparison with graph construction based on Pearson’s r, the technique used by the majority of previous studies, we find that the novel approach produces highly similar results an order of magnitude faster. Conclusions: Its demonstrated performance makes the proposed approach a sensible and efficient alternative to customary practice. An open source software package containing the created programs is freely available for download.
The Hotelling game of pure location allows interpretations in spatial competition, political theory, and professional forecasting. In this paper, the doubly symmetric mixed-strategy equilibrium for n ≥ 4 firms is characterized as the solution of a well-behaved boundary value problem. The analysis suggests that, in contrast to the cases n = 3 and n → ∞ , the equilibrium for a finite number of n ≥ 4 firms tends to overrepresent locations at the periphery of its support interval. Moreover, in the class of examples considered, an increase in the number of firms universally leads to a wider range of location choices and to a more dispersed distribution of individual locations. The results are used to comment on the potential benefit of competition in forecasting markets.
We study whether leaders influence the unethical conduct of followers. To avoid selection issues present in natural environments, we use a laboratory experiment in which we form groups and assign leadership roles at random. We study an environment in which groups compete, with dishonest behavior enhancing group earnings to the detriment of social welfare. We vary, by treatment, two instruments through which leaders can influence follower conduct-prominent statements to the group and the allocation of monetary incentives. In general, the presence of active group leaders gives rise to significantly more dishonest behavior. Moreover, appointing leaders who are likely to have acted dishonestly in a preliminary stage of the experiment yields groups with significantly more unethical conduct. The analysis of leaders' strategies reveals that leaders' statements have a stronger effect on follower behavior than the ability to distribute financial rewards, and that leaders' propensity to act dishonestly correlates with their use of statements or incentives as a means for encouraging dishonest follower conduct.
Social capital is often associated with desirable political and economic outcomes. This paper connects a growing literature on the "dark side" of social capital with institutional change. We examine the downfall of democracy in interwar Germany. Using new data on Nazi Party entry in a cross-section of cities, we show that dense networks of civic associations such as bowling clubs, choirs, and animal breeders went hand-in-hand with a more rapid rise of the Nazi Party. Towns with one standard deviation higher association density saw at least one-third faster entry. All types of associations – veteran associations and non-military clubs, "bridging" and "bonding" associations – positively predict NS Party entry. Party membership, in turn, predicts electoral success. These results suggest that social capital aided the rise of the Nazi movement that ultimately destroyed Germany's first democracy. We also show that the effects of social capital were more important in the starting phase of the Nazi movement, and in towns less sympathetic to its message.
