The vanishing viscosity limit in the presence of a porous medium

We consider the flow of a viscous, incompressible, Newtonian fluid in a perforated domain in the plane. The domain is the exterior of a regular lattice of rigid particles. We study the simultaneous limit of vanishing particle size and distance, and of vanishing viscosity. Under suitable conditions on the particle size, particle distance, and viscosity, we prove that solutions of the Navier-Stokes system in the perforated domain converges to solutions of the Euler system, modeling inviscid, incompressible flow, in the full plane. That is, the flow is not disturbed by the porous medium and becomes inviscid in the limit. Convergence is obtained in the energy norm with explicit rates of convergence

Survey of the literature on innovation and economic performance

Despite very strong differences in their treatment of technological change in economic theory, both the neoclassical and the more Schumpetarian (and evolutionary) economic approaches often assume that market selection rewards the most innovative firms. However, despite such strong assumptions, empirical evidence on whether innovative firms perform better than non-innovative firms remains inconclusive. If innovators do not grow more, does this imply that market selection fails? And does the different impact of innovation on industrial performance (measured by firm growth and profitability) and financial performance (measured by market value and stock returns) signal differences in how industrial and financial markets react to firm level efforts around innovation? This discussion paper reviews the literature on the interaction between innovation and economic/financial performance, and outlines the way that work within FINNOV Work Package 2 (SELECTION), Co-Evolution of Industry Dynamics and Financial Dynamics, will contribute to better understanding this interaction

Indices that capture creative destruction: questions and implications

The paper argues that micro and macro economists interested in the dynamics of creative destruction can gain important insights by using indices that capture the effect of innovation on the relative position of firms. This is due to the uneven and 'destructive' effect that radical innovation has on firm rankings. One such index is the market share instability index. On the financial side, the excess volatility of stock prices and idiosyncratic risk also appear to capture the uneven dynamics of creative destruction. The paper concludes by considering the implications of these propositions for economy-wide growth during periods of radical innovation (e.g. GPTs)

High growth firms, innovation and competition: the case of the US pharmaceutical industry

Innovation is key to economic growth. But firms, across sectors and regions, are highly skewed in their ability to engage with innovation, and even more skewed in their ability to translate investments in innovation into higher growth. While there was initially much attention on 'small' firms (SMEs), due to the assumption that they are more entrepreneurial and innovative, recent evidence that small firms contribute less to innovation and employment than commonly believed, has caused attention to move towards 'high growth innovative' firms (HGF). There is, however, the risk that this newly emphasized category of firms is also being 'hyped up' given how short a time period 'high growth' lasts, and how 'high growth' appears to only be important when combined with other firm specific conditions. Our paper is dedicated to exploring under what conditions high growth firms matter, in a dynamic setting over the history of the US pharmaceutical industry from 1963-2002. Following Coad and Rao (2008), we use quantile regression techniques to study the R&D-growth relationship in high growth firms compared to low growth firms. We find that the relationship is influenced by a mix of firm level characteristics including R&D intensity, R&D scale and venture capital funding. But more importantly we find that this relationship is sensitive to the changing competitive environment over the industry's history

Stock Price Volatility and Patent Citation Dynamics: the case of the pharmaceutical industry

Recent finance literature highlights the role of technological change in increasing firm specific and aggregate stock price volatility (Campbell et al. 2001, Shiller 2000, Pastor and Veronesi 2005). Yet innovation data is not used in these analyses, leaving the direct relationship between innovation and volatility untested. Our aim is to investigate more closely the relationship between stock price volatility and innovation using firm level patent citation data. The analysis builds on the empirical work by Mazzucato (2002; 2003) where it is found that stock price volatility is highest during periods in the industry life-cycle when innovation is the most '˜competence-destroying'. Here we ask whether firms which invest more in innovation (more R&D and more patents) and/or which have '˜more important' innovations (patents with more citations) experience more volatility. We focus the analysis on firms in the pharmaceutical and biotechnology industries between 1974 and 1999. Results suggest that there is a positive and significant relationship between idiosyncratic risk, R&D intensity and the various patent related measures. Preliminary support is also found for the '˜rational bubble' hypothesis linking both the level and volatility of stock prices to innovation

Innovation and Idiosyncratic Risk

The paper studies whether “idiosyncratic riskâ€, i.e. the degree to which firm and industry specific returns are more volatile than aggregate market returns, is higher in innovative industries which are characterized by more risk and uncertainty. Volatility is studied both at the industry level (for 34 different industries from 1974-2003) and at the firm level (for 5 industries with different levels of innovativeness: biotech, pharmaceuticals, computers, textile, agriculture). Findings are mixed. A relationship between innovation and volatility emerges most strongly with firm level data, when firm dimension is accounted for, and when time varying volatility is explicitly studied via GARCH analysis. The latter highlights the distinctive behavior of returns during the course of the industry life-cycle.idiosyncratic risk, volatility, innovation, industry life cycle

The Dynamics of Knowledge Accumulation, Regulation and Appropriability in the Pharma-Biotech Sector: Policy Issues

Discussion of reasons for regulation in the pharmaceutical industr

Advertising and the evolution of market structure in the US car industry

This paper focuses on a single simple stylized fact which stands out from the post-war history of the US car industry, namely that industry concentration fell just at the same time as industry advertising expenditures rose sharply. Since both events were almost certainly caused by the entry and market penetration of (largely) foreign owned car producers, this stylized fact raises interesting questions about whether – and if so, how – advertising affects entry. We use a model of consumer switching behaviour to help interpret the facts. The model predicts a simple linear association between market and advertising shares (which we observe fairly clearly at two different levels of aggregation in the data), and provides the basis for arguing that advertising can facilitate entry, but only for finite periods of time

The Impact of Millet, Sorghum, and Cowpea Research and Technology Transfer in Niger

Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies, Downloads July 2008 - June 2009: 9,