Innovation by Heterogeneous Leaders

We develop a Schumpeterian growth model in which both leaders and followers conduct R&D activities and in which leaders have different quality leads over their followers, determined by a random draw, and thus have different profit flows. We show that leaders with larger quality leads make smaller R&D investments; this result is consistent with the actual behaviors of some previous leader firms such as Sony and Eastman–Kodak. Moreover, we show that subsidizing followers’ R&D can promote leaders’ aggregate R&D, because promotion of followers’ R&D decreases (increases) the number of leaders with larger (smaller) quality leads and smaller (larger) R&D investments.* Revised： [15-30, 2015

Disruptive Innovation by Heterogeneous Incumbents and Economic Growth: When do incumbents switch to new technology?

In this paper, we construct a tractable endogenous growth model to examine heterogeneous incumbents' current technology-switching behavior. Then, we examine the effects of policies such as a subsidy for innovation by incumbents, a subsidy for innovation by entrants, and the extension of patent length. Our setting suggests interesting and counterintuitive results. High quality incumbents tend to be less likely to conduct innovation, which is inconsistent with Schumpeter's hypothesis. A subsidy for innovation by entrants decreases the average quality of differentiated goods. Moreover, it may decrease the growth rate of the economy if the positive spillover of innovation from average quality production is adequately large. Aggregate innovation can be small even when the population size is large if the barriers to entry are extremely high

Should public broadcasting companies be continued, scrambled, disbanded or privatized?

In this paper, we construct a tractable mathematical model to examine the optimal structure of a public broadcasting company. We then compare four possible scenarios from a welfare perspective: a public broadcasting company continues operating, is scrambled, is disbanded or is privatized. In our setting, the situation where only some households choose scrambling is inferior to the situation where all households pay a license fee. However, if the need for the public broadcasting company is low, it should be disbanded. Under a uniform distribution, this reference point is that more than 50% of households agree to disband the public broadcasting company; however, this percentage is crucially dependent on the shape of the distribution. Our model also suggests that privatization of a public broadcasting company is superior to disbandment if the number of commercial broadcasting company is smaller than social optimum number

Disruptive Innovation by Heterogeneous Incumbents and Economic Growth: When do incumbents switch to new technology?

In this paper, we construct a tractable endogenous growth model to examine heterogeneous incumbents' current technology-switching behavior. Then, we examine the effects of policies such as a subsidy for innovation by incumbents, a subsidy for innovation by entrants, and the extension of patent length. Our setting suggests interesting and counterintuitive results. High quality incumbents tend to be less likely to conduct innovation, which is inconsistent with Schumpeter's hypothesis. A subsidy for innovation by entrants decreases the average quality of differentiated goods. Moreover, it may decrease the growth rate of the economy if the positive spillover of innovation from average quality production is adequately large. Aggregate innovation can be small even when the population size is large if the barriers to entry are extremely high

Differentiation between non-hypervascular pancreatic neuroendocrine tumour and pancreatic ductal adenocarcinoma on dynamic computed tomography and non-enhanced magnetic resonance imaging

Purpose: To determine the differentiating features between non-hypervascular pancreatic neuroendocrine tumour (PNET) and pancreatic ductal adenocarcinoma (PDAC) on dynamic computed tomography (CT) and non-enhanced magnetic resonance imaging (MRI). Material and methods: We enrolled 102 patients with non-hypervascular PNET (n = 15) or PDAC (n = 87), who had undergone dynamic CT and non-enhanced MRI. One radiologist evaluated all images, and the results were subjected to univariate and multivariate analyses. To investigate reproducibility, a second radiologist re-evaluated features that were significantly different between PNET and PDAC on multivariate analysis. Results: Tumour margin (well-defined or ill-defined) and enhancement ratio of tumour (ERT) showed significant differences in univariate and multivariate analyses. Multivariate analysis revealed a predominance of well-defined tumour margins in non-hypervascular PNET, with an odds ratio of 168.86 (95% confidence interval [CI]: 10.62-2685.29; p < 0.001). Furthermore, ERT was significantly lower in non-hypervascular PNET than in PDAC, with an odds ratio of 85.80 (95% CI: 2.57-2860.95; p = 0.01). Sensitivity, specificity, and accuracy were 86.7%, 96.6%, and 95.1%, respectively, when the tumour margin was used as the criteria. The values for ERT were 66.7%, 98.9%, and 94.1%, respectively. In reproducibility tests, both tumour margin and ERT showed substantial agreement (margin of tumour, κ = 0.6356; ERT, intraclass correlation coefficients (ICC) = 0.6155). Conclusions: Non-hypervascular PNET showed well-defined margins and lower ERT compared to PDAC, with significant differences. Our results showed that non-hypervascular PNET can be differentiated from PDAC via dynamic CT and non-enhanced MRI

Evaluating the malignant potential of intraductal papillary mucinous neoplasms of the pancreas : added value of non-enhanced endoscopic ultrasound to supplement non-enhanced magnetic resonance imaging

Purpose: To evaluate the diagnostic performance of combining non-enhanced magnetic resonance imaging (MRI) and non-enhanced endoscopic ultrasonography (EUS) for assessing the malignant potential of lesions in patients with intraductal papillary mucinous neoplasms of the pancreas (IPMNs). Material and methods: Data from 38 patients histopathologically diagnosed with IPMN adenomas or IPMN adenocarcinomas were retrospectively analysed. Preliminary univariate and multivariate analyses were conducted to identify statistically significant associations. Three blinded radiologists evaluated the image sets to assess the diagnostic performance of combined use of non-enhanced MRI and EUS as opposed to non-enhanced MRI alone in distinguishing malignant from benign lesions. Observer performance and interobserver variability were determined using receiver-operating-characteristic curve analysis and weighted κ statistics. Results: Multivariate analyses identified a significant difference between the abrupt change in the main pancreatic duct (MPD) calibre with distal pancreatic atrophy and the signal intensity of lesion-to-spinal cord ratio on MRI; a significant difference was observed in MPD size on EUS. Diagnostic performance assessments of the image sets did not differ significantly between the blinded radiologists. Conclusions: The clinical utility of non-enhanced EUS may be attributive in evaluating IPMN that has already been evaluated by non-enhanced MRI