By representing a system of budget shares as an approximate factor model we determine its rank, i.e. the number of common functional forms, or factors, spanning the space of Engel curves. Once the common factors are estimated via approximate principal components, we identify them by imposing...

By representing a system of budget shares as an approximate factor model we determine its rank, i.e. the number of common functional forms, or factors, spanning the space of Engel curves. Once the common factors are estimated via approximate principal components, we identify them by imposing...