Ecological analysis involves analysing aggregate data for groups of individuals to make inferences about relationships at the individual level. Often the results of such analyses give badly biased estimates. This paper will consider the sources of bias in linear regression analysis using aggregate data. The role of variation of the individual level relationships between groups and the consequen...

The aim of this paper is to understand and to model claims arrival and reporting delay in general insurance. We calibrate two real individual claims data sets to the statistical model of Jewell and Norberg. One data set considers property insurance and the other one casualty insurance. For our analysis we slightly relax the model assumptions of Jewell allowing for non-stationarity so that the m...

A Working Paper is the author's intellectual property. It is intended as a means to promote research to interested readers. Its content should not be copied or hosted on any server without written permission from [email protected] Click here to access the INSEAD Working Paper collection Abstract In the newsvendor problem, a pull-to-center effect has been asserted, whereby subjects are ...

Executive Summary Data warehouses are designed to aggregate data and allow decision makers to obtain accurate, complete and up to date information. A data warehouse stands or falls on the quality of the data it contains. Most existing warehouses contain a subset of the available data and allow a limited range of queries on that data, because it is impossible to justify the cost of development o...

There are three leading explanations for the recent jobless recoveries: increasing importance of permanent shocks; long expansions creating greater need for restructuring; and structural changes that cause a shift towards adjusting labor inputs more at the intensive margin (hours) rather than the extensive margin (employment). This paper considers these competing explanations using a correlated...

There is an apparent theoretical discrepancy between the effects of monetary policy shocks on economies with differently competitive banking sectors. We employ cross-country data to investigate this hypothesis with two different approaches. First, using aggregate data we analyze the correlation between two indices: (i) a cumulative impulse response function providing an index of the effect of m...

This paper discusses a detection mechanism for malicious code through statistical analysis of opcode distributions. A total of 67 malware executables were sampled statically disassembled and their statistical opcode frequency distribution compared with the aggregate statistics of 20 non-malicious samples. We find that malware opcode distributions differ statistically significantly from non-mali...

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...