Against mashups

Martin Ravallion, the director of the development research group at the World Bank, has written a perceptive article on the dangers of “mashup indices” for the VoxEU website.

For those not familiar with statistics such indices, more politely called composite indices, combine several different factors to provide an overall index. For example, the United Nations Human Development Index (HDI) combines life expectancy, schooling and income to make an overall index of well-being.

The obvious problem with such indices is that they pull together lots of diverse elements. For instance, in relation to the construction of the HDI some statistical jiggery-pokery was needed to combine life expectancy (measured in years), schooling (percentage literacy or enrolment rates) and GDP per head.

For me a good example of a dubious mashup index was Unicef’s attempt to construct an international league table of child well-being. Few media reports looked closely at the hotch-potch of different factors included in the index.

Perhaps even more absurd is Newsweek magazine’s recent league table of the “best countries in the world”. It is based on a mashup of mashups – combining many mashup indices together.

Even more elaborate mashups are being released along with the 20th anniversary edition of the Human Development Report on 4 November.