  We propose a model-based vulnerability index of the population from Uruguay
to vector-borne diseases. We have available measurements of a set of variables
in the census tract level of the 19 Departmental capitals of Uruguay. In
particular, we propose an index that combines different sources of information
via a set of micro-environmental indicators and geographical location in the
country. Our index is based on a new class of spatially hierarchical factor
models that explicitly account for the different levels of hierarchy in the
country, such as census tracts within the city level, and cities in the country
level. We compare our approach with that obtained when data are aggregated in
the city level. We show that our proposal outperforms current and standard
approaches, which fail to properly account for discrepancies in the region
sizes, for example, number of census tracts. We also show that data aggregation
can seriously affect the estimation of the cities vulnerability rankings under
benchmark models.
