

You may be right, but as with the trucks, I would expect a much less sharp minima: Smartphone and instant messaging adoption didn’t happen all at once, but from this graph we see that we’re going from a substantial year-on-year decrease directly to a large year-on-year increase. A change that is gradually adopted over the course of several years can’t really cause that kind of effect.







I think it makes sense to be flexible: In a table, or other bureaucratic contexts, it makes sense to put the family name first. In daily speech, it’s rather common that I’m in contact with family members (even more so historically), and it makes most sense to use the distinguishing name (first name) first.
If I’m with a group that includes siblings or parents/children, I can usually distinguish everyone by first name, while many people share last names.