Advertising claims that don't always mean what they seem to mean

While watching (sporadically) Monday Night Football and reading John LeCarre's The Lookingglass War, I noticed a claim by Toyota: "80% of all Toyotas sold over the past 20 years are still on the road."

And just what do they want you to think? Well, one possibility is that they want you to think that 80% of the Toyotas sold in (not just since)1990 are still on the road.

Suppose that Toyota's sales have increased at a constant 5% per year over the part 20 years. Then, it's possible that the oldest Toyotas still on the road were sold 14 years ago.

(The faster the rate of growth in sales, the closer in the past 80% of the sales would be; at 7% per year sales growth, it'd take only the last 13 years.)

I guess the moral of this is to be wary of advertising claims. (Did anyone need to learn that? I hope not.)