This paper examines an economy in which aggregate shocks are not dispersed equally throughout the population. Instead, while these shocks affect all individuals ex ante, they are concentrated among a few ex post. The equity premium in genera) depends on the concentration of these aggregate shocks; it follows that one cannot estimate the degree of risk aversion from aggregate data alone. These f...

In this paper we present a new approach for studying aggregations in the context of database query languages. Starting from a broad de nition of aggregate function, we address our investigation from two di erent perspectives. We rst propose a declarative notion of uniform aggregate function that refers to a family of scalar functions uniformly constructed over a vocabulary of basic operators by...

In this paper we introduce generalized projections (GP s), an extension of duplicateeliminating projections, that capture aggregations, groupbys, duplicate-eliminating projections (distinct), and duplicate-preserving projections in a common uni ed framework. Using GP s we extend well known and simple algorithms for SQL queries that use distinct projections to derive algorithms for queries using...

The exchange rate plays an essential role for firms which export goods and import raw materials. In this paper, the effects of real specific exchange rate fluctuations in imports, exports and aggregate trade on industry sector, chemical and transportation industries outputs in 49 OIC countries were investigated by using a panel data model over 1990-2014. Particularly, this paper presents eviden...

Unlike infrastructure-based counterparts, services and applications of future infrastructure-less mobile networks highly depend on the mobility patterns of wireless device carriers. Analyzing and modeling their mobility is essential in precise performance evaluation of these opportunistic networks, where inter-contacts are taken advantage of as opportunities for message forwarding. Recently, th...

We propose an extension of Datalog that supports aggregates under set semantics and is as expressive as the previous extensions of Datalog which use bag semantics to represent aggregate programs. We show that under set semantics, our extension has greater expressive power than the previous extensions of Datalog which support aggregates. By expressing aggregate Datalog queries under set semantic...

A classical problem in database theory is to verify whether there exists a relation (or database) instance satisfying a number of given dependency constraints but the issue of handling constraints on aggregate data has not been much investigated so far. This paper introduces a new type of data dependency, called count constraint, that requires the results of given count operations on a relation...