Quo Vadis, Action Recognition? A New Model and the Kinetics Dataset

The paucity of videos in current action classification datasets (UCF-101 and HMDB-51) has made it difficult to identify good video architectures, as most methods obtain similar performance on existing small-scale benchmarks. This paper re-evaluates state-of-the-art architectures in light of the new Kinetics Human Action Video dataset. Kinetics has two orders of magnitude more data, with 400 human action classes and over 400 clips per class, and is collected from realistic, challenging YouTube videos. We provide an analysis on how current architectures fare on the task of action classification on this dataset and how much performance improves on the smaller benchmark datasets after pre-training on Kinetics. We also introduce a new Two-Stream Inflated 3D ConvNet (I3D) that is based on 2D ConvNet inflation: filters and pooling kernels of very deep image classification ConvNets are expanded into 3D, making it possible to learn seamless spatio-temporal feature extractors from video while leveraging successful ImageNet architecture designs and even their parameters. We show that, after pre-training on Kinetics, I3D models considerably improve upon the state-of-the-art in action classification, reaching 80.9% on HMDB-51 and 98.0% on UCF-101.Comment: Removed references to mini-kinetics dataset that was never made publicly available and repeated all experiments on the full Kinetics datase

No Deep Pockets: Some stylized results on firms' financial constraints

This paper is a brief survey of recent empirical work on financial constraints faced by firms. It is organized as a series of stylized results which mirror what is generally understood about severity of financial constraints and effects that they have upon firms. This survey shows that (a) the financial constraint is a widespread key concern for firms, hindering their ability to carry out their optimal investment and growth trajectories and (b) the severity of such constraints depends on institutional and firm specific characteristics, as well as on the nature of investment projects.Firms’ financial constraints; Firm-level studies.

The Shadow of Death: Analysing the Pre-Exit Productivity of Portuguese Manufacturing Firms

In this study, we examine the pre-exiting productivity profile of mature firms relatively to survivors. We also evaluate how productivity affects the probability of exit along various dimensions. Our approach is an empirical one, and it is based on an unbalanced panel of Portuguese manufacturing firms covering a period of one decade. Our findings confirm that market selection forces low-productivity firms to exit, but there is also evidence that a sizeable portion of low-productivity firms do not shut down. Conversely, there is a non-negligible fraction of high-productivity firms that do actually close. In line, too, with some key theoretical predictions, exiting firms reveal a falling productivity level over a number of years prior to exit. Finally, our results from the survival model show that both low-productivity and small firms are much more likely to exit the market. Industry and macro environment were also found to have a non-negligible role on the exit of mature firms.Pre-exit performance; Exit pattern; Productivity; Firm survival; Portugal

Does Schumpeterian Creative Destruction Lead to Higher Productivity? The effects of firms’ entry

This paper discusses the impact of newly created firms on industry productivity growth. Our central hypothesis is that there are two potential effects of new firms on productivity growth: a direct effect, as entrants may be relatively more productive than established firms; and an indirect effect, through increased competitive pressure that stimulates incumbents to elevate their productivity in order to survive. The results of the decomposition exercise of aggregate productivity growth suggest that the direct contribution of entry is small. In turn, the regression analysis on the effect of entry on productivity growth of incumbents indicates that the higher is the former, the higher is the latter, which is equivalent to say that the greater is the competitive pressure generated by new entrants, the higher is the expected aggregate productivity level.Entry, Firm dynamics, Productivity growth, Competition effect