Stochastic Trade Networks

This paper develops a simple network model to describe the dynamic of the intensive and extensive margin of international trade flows. The result is achieved by means of the combination of two mechanisms of proportional growth: the first (discrete) determines the formation of trade links, the second (continuous) governs trade intensity. We show that our setup is able to simultaneously match a large number of empirical regularities, such as the fraction of zero trade flows across pairs of countries or the high concentration of trade with respect to both products and destinations. Our findings suggest that stylized facts are strongly interconnected across different levels of aggregation of trade data , so that a unifying explanation is called for. By incorporating stochastic elements into standard trade models we can improve their ability to explain relevant facts about world trade

Technological Regimes and the Growth of Networks An Empirical Analysis

This paper shows how specific technological and relational regimes have shaped the growth of the network of R&D collaborative agreements in pharmaceuticals in the 1990s. Our analysis reveals the existence of a complex set of regimes of firm growth within the network, providing additional evidence supporting prediction that both growth and innovative activities of large and small firms respond, even within a given industry, to considerably different technological and economic factors. Moreover, the paper shows, in the context of a specific industry and by means of a series of preliminary and explorative empirical analyses, that information on the topological properties of a given industrial settings and on roles/positions of organizations within it can be used to disentangle some fundamental generative processes underlying observed processes of growth. This result contributes to the 'old' stochastic approach to firm growth, in the direction of building parsimonious and, at the same time, more realistic, representations of processes of industrial growth.-

Market Structure and Drug Innovation

An explosion of knowledge and a growing array of tools and technologies have transformed modern drug R&D, while its cost has risen by a sizable amount. At the same time, the unchecked increase in health care and prescription drug spending has spawned cost containment policies that are restricting the demand for drugs in all major markets. This Perspective explores the interplay between technological advances and regulatory policies and their likely impact on the dynamics of the pharmaceutical industry. Advances in the life sciences have profoundly transformed the drug research and development (R&D) process. That transformation has come at a price, boosting the cost of developing a new molecular entity (NME) to 802 million by 2000. More expensive R&D, combined with an aging population and better diagnostic techniques, has swelled drug spending in the United States, which reached 141 billion in 2001. These increases have in turn induced a spate of cost containment measures that are affecting demand for pharmaceuticals in all major markets. This Perspective considers the impact of the interplay between technological advances and health care policy on the future dynamics of the pharmaceutical industry.Pharmaceutical Industry, R&D Productivity, Health Care Policy

Innovation and corporate dynamics: a theoretical framework

We provide a detailed analysis of a generalized proportional growth model (GPGM) of innovation and corporate dynamics that encompasses the Gibrat’s Law of Proportionate Effect and the Simon growth process as particular instances. The predictions of the model are derived in terms of (i) firm size distribution, (ii) the distribution of firm growth rates, and (iii-iv) the relationships between firm size and the mean and variance of firm growth rates. We test the model against data from the worldwide pharmaceutical industry and find its predictions to be in good agreement with empirical evidence on all four dimensions

Missing Links in Multiple Trade Networks

In this paper we develop a network model of international trade which is able to replicate the concentrated and sparse nature of trade data. Our model extends the preferential attachment (PA) growth model to the case of multiple networks. Countries trade a variety of goods of different complexity. Every country progressively evolves from trading less sophisticated to high-tech goods. The probability to capture more trade opportunities at a given level of complexity and to start trading more complex goods are both proportional to the number of existing trade links. We provide a set of theoretical predictions and simulative results. A calibration exercise shows that our model replicates the same concentration level of world trade as well as the sparsity pattern of the trade matrix. Moreover, we find a lower bound for the share of genuine missing trade links. We also discuss a set of numerical solutions to deal with large multiple networks

R&D, Within and Between Patent Competition in the Pharmaceutical Industry

We analyse the consequences of the increasing complexity of R&D on within- and between-patent competition in the pharmaceutical industry. The intensity of competition is measured by jointly considering the timing from market launch to patent expiry, the strength of between-patent competition as well as competition introduced by generic producers. A simple model is proposed that predicts the shrinking of product lifetimes in the presence of correlated parallel R&D projects and market portfolios. The model is tested using data on pharmaceutical products sold in Europe and in the US. Based on our model we are able to estimate the impact of R&D complexity and relatedness among R&D portfolios on the value of innovative drugs

Dynamic Competition in Pharmaceuticals: Patent Expiry, Generic Penetration, and Industry Structure

This paper investigates patterns of industrial dynamics and competition in the pharmaceutical industry, with particular reference to the consequences of patent expiry in different countries. We focus on the competition at the level of single chemical entities, distinguishing between original brands and generic products. Quarterly data, spanning from July 1987 to December 1998, on sales of pharmaceutical products in four countries (USA, UK, Germany, and France) constitute the basis of our analysis. All the products containing major molecules whose patent expiration date lies between 1986 and 1996 are included in our sample. We show how diffusion of generics is linked to the characteristics of the market and investigate how price dynamics of original products are affected by generic competition. Our empirical investigation shows that the dynamics of drug prices and the competition by generic drugs vary significantly across countries. This heterogeneity notwithstanding, a clear distinction seems to emerge. On the one hand, systems that rely on market-based competition in pharmaceuticals promote a clear distinction between firms that act as innovators and firms that act as imitators after patent expiry. Here, original products enjoy premium prices and exclusivity profits under patent protection, and face fierce price competition after patent expiry. On the other hand, in systems that rely on administered prices, penetration by generic drugs tends to be rather limited. Its descriptive and preliminary nature notwithstanding, our analysis seems to have relevant implications at different levels of generality, especially for Europe.Pharmaceuticals; Patent expiration; Off-patent competition

Co-experience Network Dynamics: Lessons from the Dance Floor.

Experience and socialization are key factors in determining customer commitment and renewal decisions in the service sector. To analyse the combined effect of experience and socialization, in this paper we introduce the concept of co-experience networks. A new methodological approach, originally applied in the field of social ethology, is devised to study reality-mined co-experience networks. By analysing a network of health club members over four years, we find that long-experienced clients have a lower chance to renew their contracts. On the other hand, central members in the co-experience network are stable and tend to renew their memberships. Further, since the members of the same reference group align their levels of commitment, renewal decisions are clustered in a small-world network. These findings contribute to our understanding of social dynamics and localized conformity in customer decision-making that can be used to plan marketing strategies to improve customer retention.