It's not always easy to make this judgment, but you do have to differentiate the normal process of expansion in a city that is expanding from the more general situation where people become worried about being left behind and feel that they must have the “most house” they can possibly lay their hands on.
Il n'est pas toujours facile de bien voir la différence, mais il faut distinguer entre l'expansion normale d'une ville et la situation plus générale où les gens ont peur de perdre du terrain et estiment qu'ils doivent acheter «le plus de maison possible».