How many people aged 20 to 39 do you talk to in a week?
Random epidemiology table.

Some authors from the Netherlands tried to improve estimates of the transmission of respiratory infections, by asking their study population: How many people did you have face-to-face conversations with during the past week? They asked this question separately for each age group: that is, the 20-39 year olds (e.g.) got asked how many people in each of the separate age groups (1-5, 6-12, 13-19, 20-39, 40-59, 60 or over) they had spoken to. This was done in Utrecht; see if your estimate matches theirs.