Title: Ratings and rankings: Voodoo or Science?
Authors: PARUOLO PaoloSAISANA MichaelaSALTELLI Andrea
Citation: JOURNAL OF THE ROYAL STATISTICAL SOCIETY SERIES A-STATISTICS IN SOCIETY vol. 176 no. 3 p. 609-634
Publisher: WILEY-BLACKWELL
Publication Year: 2013
JRC Publication N°: JRC64676
ISSN: 0964-1998
URI: http://onlinelibrary.wiley.com/doi/10.1111/j.1467-985X.2012.01059.x/pdf
http://publications.jrc.ec.europa.eu/repository/handle/JRC64676
DOI: 10.1111/j.1467-985X.2012.01059.x
Type: Articles in Journals
Abstract: Composite indicators aggregate a set of variables using weights which are understood to reflect the variables’ importance in the index. In this paper we propose to measure the importance of a given variable within existing composite indicators via Karl Pearson’s ‘correlation ratio’; we call this measure ‘main effect’. Because socio-economic variables are heteroskedastic and correlated, (relative) nominal weights are hardly ever found to match (relative) main effects; we propose to summarize their discrepancy with a divergence measure. We further discuss to what extent the mapping from nominal weights to main effects can be inverted. This analysis is applied to five composite indicators, including the Human Development Index and two popular league tables of university performance. It is found that in many cases the declared importance of single indicators and their main effect are very different, and that the data correlation structure often prevents developers from obtaining the stated importance, even when modifying the nominal weights in the set of nonnegative numbers with unit sum.
JRC Institute:Institute for the Protection and Security of the Citizen

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