A new family of posets generalizing the weak order on some Coxeter groups

We construct a poset from a simple acyclic digraph together with a valuation on its vertices, and we compute the values of its M\"obius function. We show that the weak order on Coxeter groups of type A, B, affine A, and the flag weak order on the wreath product $\mathbb{Z} \_r \wr S\_n$ introduced by Adin, Brenti and Roichman, are special instances of our construction. We conclude by associating a quasi-symmetric function to each element of these posets. In the $A$ and $\widetilde{A}$ cases, this function coincides respectively with the classical Stanley symmetric function, and with Lam's affine generalization

The transition to consumption taxation, part 1: the impact on existing capital

Alan Viard reviews the transitional impact on existing capital from replacing the income tax with a consumption tax. This replacement generally reduces the real value of existing capital because it does not receive the tax relief given to new investment. If the income and consumption taxes had stylized forms and capital were produced without adjustment costs, the proportional decline would equal the consumption tax rate--a 25 percent tax would uniformly reduce the value of existing capital by 25 percent. Under more realistic assumptions, however, the actual decline is likely to be smaller and less uniform and some types of capital may even increase in value. The burden on owners of existing capital is also mitigated because the tax reform increases the rate of return they earn from reinvestment.

The effect of Beijing’s driving restrictions on pollution and economic activity

We evaluate the environmental and economic effects of Beijing’s driving restrictions. Based on daily data from multiple monitoring stations, air pollution falls 19% during every-other-day and 8% during one-day-per-week restrictions. Based on hourly viewership data, the number of television viewers during the restrictions increases 1.7 to 2.3% for workers with discretionary work time but is unaffected for workers without, consistent with the restrictions’ higher per-day commute costs reducing daily labor. Causal effects are identified from both time-series and spatial variation in air quality and intra-day variation in viewership. We provide possible reasons for the policy’s success, including evidence of high compliance based on parking garage entrance records. Our results contrast with previous findings of no pollution reductions from driving restrictions and provide new evidence on commute costs and labor supply.Driving restrictions; externalities; environmental economics; pollution

A natural generalization of Balanced Tableaux

We introduce the notion of "type" of a tableau, that allows us to define new families of tableaux including both balanced and standard Young tableaux. We use these new objects to describe the set of reduced decompositions of any permutation. We then generalize the work of Fomin \emph{et al.} by giving, among other things, a new proof of the fact that balanced and standard tableaux are equinumerous, and by exhibiting many new families of tableaux having similar combinatorial properties to those of balanced tableaux.Comment: This new version cointains several major changes in order to take new results into accoun

Pricing of Complementary Goods and Network Effects

We discuss the case of a monopolist of a base good in the presence of complementary goods provided either by it or by other firms. We assess and calibrate the extent of the influence on the profits from the base good that is created by the existence of complementary goods, i.e., the extent of the network effect. We establish an equivalence between a model of a base and a complementary good and a reduced-form model of the base good in which network effects are assumed in the consumers’ utility functions as a surrogate for the presence of complementary goods produced by others. We also assess and calibrate the influence on profits of the intensity of network effects and quality improvements in both goods. We evaluate the incentive that a monopolist of the base good has to improve its quality rather than that of complementary goods. Finally, based on our results, we discuss an explanation of the fact that Microsoft Office has a significantly higher price than Microsoft Windows although both products have comparable market shares.calibration; monopoly; network effects; complementary goods; software; Microsoft

Computing maximal cliques in link streams

A link stream is a collection of triplets $(t, u, v)$ indicating that an interaction occurred between u and v at time t. We generalize the classical notion of cliques in graphs to such link streams: for a given $\Delta$, a $\Delta$-clique is a set of nodes and a time interval such that all pairs of nodes in this set interact at least once during each sub-interval of duration $\Delta$. We propose an algorithm to enumerate all maximal (in terms of nodes or time interval) cliques of a link stream, and illustrate its practical relevance on a real-world contact trace

Pricing of Complementary Goods and Network Effects*

We discuss the case of a monopolist of a base good in the presence of a complementary good provided either by it or by another firm. We assess and calibrate the extent of the influence on the profits from the base good that is created by the existence of the complementary good, i.e., the extent of the network effect. We establish an equivalence between a model of a base and a complementary good and a reduced-form model of the base good in which network effects are assumed in the consumers’ utility functions as a surrogate for the presence of direct or indirect network effects, such as complementary goods produced by other firms. We also assess and calibrate the influence on profits of the intensity of network effects and quality improvements in both goods. We evaluate the incentive that a monopolist of the base good has to improve its quality rather than that of the complementary good under different market structures. Finally, based on our results, we discuss a possible explanation of the fact that Microsoft Office has a significantly higher price than Microsoft Windows although both products have comparable market shares.calibration; monopoly; network effects; complementary goods; software; Microsoft