Behind me is the Dente del Giante, or Giant’s Tooth, in Italy. I told our guide that it looked more like a thumb to me. That started me thinking about apartments and useful rules-of-thumb investors can use. For example: The economic news always focuses on the unemployment rate. I don’t want to sound cold and uncaring, but that’s not the most important statistic right now. At least it isn’t for apartment investors who want to figure out what will happen to vacancies and rents.