+0 little migration or tourism, expats often “strange” and “unusual”
+1 Some local tourism, resorts, vacations, occasional foreign tourism
+2 Much foreign tourism, semi-permanent internal migrants seeking work
+3 Major border-country/regional traffic hub, diasporas often seen
+4 International (other regions) migration, business, illegals
+5 Top, global destination for migrants, tourists, business
+1 would be for local tourists (and some foreign). +2 is more where foreign tourism begins to get into play, and foreign business. +3 means you’re seeing significant internal migration and migrants from surrounding countries. +4 means that if your in Asia, you’re probably seeing migrants from all over Asia and some other regions (Africa, Europe). +5 is the top of the top, a hub for business, pilgrims, tourists, migrants, the works. +5 probably wouldn’t be assigned to more than about… 1% of cities?