Natural and Sophisticated Meaning of Language
There are two natural ways to describe your age between age 40 and 49. One is vague, 40 to 44 being "early 40's" and 45 to 49 being "late 40's." The other one is precise, 40 to 42 being "barely in 40's", 43 to 47 being "mid 40's," and 48 to 49 being "almost 50." Imagine you can make one statement about your age, but can use only one term and can't lie. Then, regardless of your age, you can choose one out of exactly two terms to talk about your age. For example, if you are 44, you can be vague and say that you are in early 40's or you can be precise and say you are in mid 40's. Similarly, if you are 47, you can say you are in late 40's or you are in mid 40's. Naturally, your want to make the listener think you are as young as possible. However, the listener is sophisticated and understand what you are trying to do.
It is easy to see that you would not always be vague or always be precise when you describe your age. Suppose you are always vague and this is expected by the listener. Then, if you are actually 42, you would instead be precise and declare you are barely in 40's. Since only people from 40 to 42 can use this term, you would convince the listener that you are the average of 40 to 42, which is younger than the average of 40 and 44 that the listener would infer when you say you are in the early 40's. Now, suppose you are always precise and the listener expects this. Then, if you are actually 44, you would instead be vague and declare you are in early 40's. Since the only age group that could possibly make such declaration and benefit from it are those from 43 to 44, saying you are in early 40's would convince the listener that you are the average of 43 to 44, which is younger than the average of 43 to 47 that the listener would infer when you say you are in the mid 40's.
What arises in this situation is the following sophisticated "norm" of speaking about your age. If you are from 40 and 42, declare that you are barely in 40's; from 43 to 44, declare that you are in early 40's; from 45 to 47, declare that you are in mid 40's; and from 48 to 49, declare you are in late 40's. The only term you would never use is almost 50. You could only make such declaration when you are actually from 48 and 49, but given that the listener expects people in this age group to say instead they in late 40's, you would not benefit from saying you are almost 50. Indeed, if the listener sometimes is gullible and applies the natural meaning of late 40's, you would strictly prefer to follow the norm and be vague about your age.
In the above norm of using the language, the natural meaning does not always correspond to the sophisticated meaning. In particular, the norm includes vague terms that are intended to exploit any naivety on the part of the listener, even though a sophisticated one is never fooled. A vague declaration of being in early 40's in fact informs a sophisticated listener that you are really from 43 to 44. Furthermore, some precise terms become even more informative about the actual age. Declaring that you are in mid 40's informs a sophisticated listener that you are really from 45 to 47, as opposed to the natural meaning of from 43 to 47. So the sophisticated meaning of the language is quite subtle. Indeed, you have to switch between being precise and being vague as you age, and certainly not only old folks are vague about their age!