Financial asset returns are known to be conditionally heteroskedastic and generally non-normally distributed, fat-tailed and often skewed. In order to account for both the skewness and the excess kurtosis in returns, we combine the BEKK model from the multivariate GARCH literature with different...

We analyze the incentives of internet service providers (ISPs) to break net neutrality by excluding internet applications competing with their own products, a typical example being the exclusion of VoIP applications by telecom companies offering internet and voice services. Exclusion is not a...

We start by using various economic and pedagogical concepts to understand the specificities of MOOC (Massive Online Open Courses) platforms. We then discuss how the private provision of MOOCs, seen as pure public goods, can be sustained. Based on the theory of multisided platforms, we analyse...

The exact nonnegative matrix factorization (exact NMF) problem is the following: given an m-by-n nonnegative matrix X and a factorization rank r, find, if possible, an m-by-r nonnegative matrix W and an r-by-n nonnegative matrix H such that X = WH. In this paper, we propose two heuristics for...

Markov-switching models are usually specified under the assumption that all the parameters change when a regime switch occurs. Relaxing this hypothesis and being able to detect which parameters evolve over time is relevant for interpreting the changes in the dynamics of the series, for...

Expanding variety and the number of offered products is attractive for a firm to fit customer needs. Nevertheless, the greater complexity and the proliferation of stock-keeping units (SKUs) without substantial differentiation may not substantially improve customer satisfaction while raising...

We propose a general model of monopolistic competition, which encompasses existing models while being flexible enough to take into account new demand and competition features. The basic tool we use to study the market outcome is the elasticity of substitution at a symmetric consumption pattern,...

We present the Fair Social Ordering approach to policy assessment. In an economic model, a Social Ordering Function (SOF) associates each economy in the domain with a complete ranking of the allocations. We describe the main achievements of the SOF theory. We present two applications, which show...

We study the macroeconomic effects of systemic bank runs in a neoclassical model with a microfounded banking system. In every period, the banks provide insurance against some idiosyncratic liquidity shocks, but the possibility of sunspot-driven bank runs distorts the equilibrium allocation. In a...

We solve two related extremal problems in the theory of permutations. A set Q of permutations of the integers 1 to n is inversion-complete (resp., pair-complete) if for every inversion (j, i), where 1 <= i < j <= n, (resp., for every pair (i, j), where i not= j) there exists a permutation in Q where j is before i. It is minimally inversion-complete if in addition no proper subset of Q is inversion-complete; and similarly for paircompleteness. The problems we consider are to determine the maximum cardinality of a minimal inversion-complete set of permutations, and that of a minimal pair-complete set of permutations. The latter problem arises in the determination of the Carathéodory numbers for certain abstract convexity structures on the (n - 1)-dimensional real and integer vector spaces. Using Mantel's Theorem on the maximum number of edges in a triangle-free graph, we determine these two maximum cardinalities and we present a complete description of the optimal sets of permutations for each problem. Perhaps surprisingly (since there are twice as many pairs to cover as inversions), these two maximum cardinalities coincide whenever n >= 4.