I live in a duplex, and over the past few years I have had three sets of neighbours: the girls who exercised, the family of wrestlers, and the smooth-playing horn-man.
These neighbours have NOTHING in common except for one bizarre trait: they all decide to adopt dogs halfway through their tenancy.
Why? I don't know. If I were to use my neighbours as a representative sample I'd have to assume that everybody in the world owns a dog.