Iván Isaias is meant to be buying the groceries at the Wal-Mart Supercenter in Buenavista, a central neighbourhood of Mexico City. Instead, he and Olimpia, his girlfriend, are in the supermarket’s electronics department eyeing shelves full of hi-fi equipment with flashing lights and heavy price tags.

A decade ago, high interest rates and a lack of credit would have made it almost impossible for Mexicans such as Mr Isaias, a 19-year-old with a full-time job at McDonald’s and part-time work as a clown, to contemplate buying the Sony system he is about to put in his shopping trolley.