Issues in the analysis of co-authorship networks

Scientific collaboration is a complex phenomenon that improves the sharing of competences and the production of new scientific knowledge. Social Network Analysis is often used to describe the scientific collaboration patterns defined by co-authorship relationships. Different phases of the analysis of collaboration are related to: data collection, network boundary setting, relational data matrix definition, data analysis and interpretation of results. The aim of this paper is to point out some issues that arise in these different phases, highlighting: (i) the use of local archives versus international bibliographic databases; (ii) the use of different approaches for setting boundaries in a whole-network; (iii) the definition of a co-authorship data matrix (binary and weighted ties) and (iv) the analysis and the interpretation of network measures for co-authorship data. We discuss the different choices that can be made in these phases within an illustrative example on real data which is referred to scientific collaboration among researchers affiliated to an academic institution. In particular, we compare global and actor-level network measures computed from binary and weighted co-authorship networks in different disciplines.     

Optimal strategies in linear multisector models: Value function and optimality conditions

In this paper we study an optimal control problem with mixed constraints related to a multisector linear model with endogenous growth. The main aim is to establish a set of necessary and a set of sufficient conditions which are the basis for studying the qualitative properties of optimal trajectories. The presence of possibly degenerate mixed constraints, the unboundedness and non-strict convexity of the Hamiltonian, make the problem difficult to deal with. We develop first the dynamic programming approach, proving that the value function is a bilateral viscosity solution to the associated Hamilton–Jacobi–Bellman (HJB) equation. Then, using our results, we give a set of sufficient and a set of necessary optimality conditions which involve so-called co-state inclusion: this can be interpreted as the existence of a dual path of prices supporting the optimal path.     

Partnership,reciprocity and team design

This paper studies the effect of intention-based reciprocity preferences on the free-riding problem arising in partnerships. Our results suggest a tendency of efficient partnerships to consist of members whose sensitivity to reciprocity is – individually or jointly – sufficiently high. Sufficient conditions for the implementation of the efficient strategy profile require a reciprocity-based sharing rule so that each partner gets a fraction of the output, which is a percentage of his own sensitivity to reciprocity with respect to the overall sensitivity in the team. Finally, we introduce the concept of psychological strong Nash equilibrium and show that it allows for the unique and collusion-proof implementation of the efficient strategy profile.     

Internal and external factors in innovation persistence

This paper contributes to the analysis of the persistence of innovation activities, as measured by total factor productivity (TFP), and explores its internal and external determinants stressing its path-dependent characteristics. The external conditions, namely the quality of local knowledge pools and the strength of the Schumpeterian rivalry, along with the internal conditions (the actual levels of dynamic capabilities, as proxied by wage levels and firm size) exert a specific and localised effect upon the persistent introduction of innovations. A multiple transition probability matrixes (MTPMs) approach has been implemented to capture the contingent effects of external factors on long-term innovation persistence. The empirical analysis of the dynamics of firm-level TFP for a sample of approximately 7000 Italian manufacturing companies observed during the years 1996–2005 is based on both the comparison of different transition probability matrixes and on dynamic discrete choice panel data models. The evidence provided by the test of MTPMs in sub-periods suggests that innovation persistence is path-dependent, as opposed to past-dependent.     

Consistent inference in fixed-effects stochastic frontier models

The classical stochastic frontier panel data models provide no mechanism to disentangle individual time invariant unobserved heterogeneity from inefficiency. Greene (2005a, b) proposed the so-called “true” fixed-effects specification that distinguishes these two latent components. However, due to the incidental parameters problem, his maximum likelihood estimator may lead to biased variance estimates. We propose two alternative estimators that achieve consistency for $n\to \infty$ with fixed $T$. Furthermore, we extend the Chen et al. (2014) results providing a feasible estimator when the inefficiency is heteroskedastic and follows a first-order autoregressive process. We investigate the behavior of the proposed estimators through Monte Carlo simulations showing good finite sample properties, especially in small samples. An application to hospitals’ technical efficiency illustrates the usefulness of the new approach.     

SHIFTING BOUNDARIES IN ECONOMICS: THE INSTITUTIONAL COGNITIVE STRAND AND THE FUTURE OF INSTITUTIONAL ECONOMICS

This paper aims at contributing to the debate on the future of institutional economics and of the field as a whole by starting from the literature that discusses the relationship between Old‐Original Institutional Economics and New Institutional Economics. It suggests that the process of reunifying OIE and NIE (and evolutionary economics) prompted by part of the literature could be improved by the contribution of the Cognitive Institutional Economics. The paper follows a two‐stage pathway: first, it frames the debate on the relationships between NIE and the OIE and it concentrates on a subset of the literature that shows that NIE's recent developments complicate the distinction between NIE and OIE, and it explores the possibility that NIE and OIE may merge so that an amalgam of NIE, OIE and Evolutionary Economics becomes the next economic paradigm. Secondly, the paper argues that a step forward in the direction outlined by the literature has been made by CIE, which is a research stream that developed from cross‐fertilization among NIE, OIE and the Hayekian contributions to the analysis of institutions. In the concluding remarks, the possible emergence of a single institutional paradigm is discussed in the light of the literature about change in economics.     

Co‐integration Rank Determination in Partial Systems Using Information Criteria

We investigate the asymptotic and finite sample properties of the most widely used information criteria for co‐integration rank determination in ‘partial’ systems, i.e. in co‐integrated vector autoregressive (VAR) models where a sub‐set of variables of interest is modelled conditional on another sub‐set of variables. The asymptotic properties of the Akaike information criterion (AIC), the Bayesian information criterion (BIC) and the Hannan–Quinn information criterion (HQC) are established, and consistency of BIC and HQC is proved. Notably, the consistency of BIC and HQC is robust to violations of weak exogeneity of the conditioning variables with respect to the co‐integration parameters. More precisely, BIC and HQC recover the true co‐integration rank from the partial system analysis also when the conditional model does not convey all information about the co‐integration parameters. This result opens up interesting possibilities for practitioners who can now determine the co‐integration rank in partial systems without being concerned about the weak exogeneity of the conditioning variables. A Monte Carlo experiment based on a large dimensional data generating process shows that BIC and HQC applied in partial systems perform reasonably well in small samples and comparatively better than ‘traditional’ methods for co‐integration rank determination. We further show the usefulness of our approach and the benefits of the conditional system analysis in two empirical illustrations, both based on the estimation of VAR systems on US quarterly data. Overall, our analysis shows the gains of combining information criteria with partial system analysis.     

Assessing excess liquidity in the euro area: the role of sectoral distribution of money

The strong and prolonged deviation of money growth from its reference value since 2001 has caused concern among policy-makers about the upside risks to price stability from monetary developments. In this article we provide evidence that these risks might have been smaller until 2005 than regularly assumed. Three basic findings support this view. First, a sectoral breakdown of money holdings shows that current excess liquidity conditions have been partly related to the acceleration of nonbank financial intermediaries’ money demand, as well as to the accumulation of marketable instruments. Such increases are likely to be associated more to portfolio choices than to transaction motives. Second, evidence from balance sheet data on investment funds points to a general increase in the relative importance of this sector in the economy, rather than to a higher degree of liquidity of their asset positions, thus reflecting, to a large extent, a permanent change in the financial structure of the economy. Third, excess liquidity measures that exclude nonbank financial intermediaries’ money holdings have more predictive power for future inflation at medium-term horizons than those that include them.     

Does trade credit redistribution thwart monetary policy? Evidence from Italy

Italy is an ideal candidate for testing the credit view of the transmission mechanism because of a bank-centred financial structure, a sizeable trade debt, and an economy titled towards small firms. An empirical analysis of trade credit and debt on averaged panel data shows that small firms act as financially constrained and cycle-sensitive, whereas large ones aim at smoothing sales, adopt an integrated management of inventories and receivables and have a higher trade debt to purchases elasticity. On balance, the net trade credit channel does not, as implied by the credit view, shield small firms from a monetary squeeze.     

Formal and informal external linkages and firms�� innovative strategies. A cross-country comparison

Firms increasingly rely upon external actors for their innovation process. Interaction with these actors may occur formally (i.e. through a collaboration agreement) or informally (i.e. external actors acts as sources of information). We analyze the reasons why firms consider it to be important to develop formal and informal external linkages in the innovation process by looking at the role played by firms’ innovative strategies and by taking into account the possibility that a complementarity or substitutive relationship might exist between formal and informal linkages. Data are from the Third Community Innovation Survey (CIS 3), where we have access to firm level micro-data from Sweden, Norway, the Netherlands and the UK.