Absolutely, you're right. We did it for official languages in minority communities. We even compared the age pyramid or age structure between 1971 and 2016, and it changed completely, because, over time, the population is aging, and the language is not being transmitted fully to their children, mostly because of the fact that there are mixed couples, exogamy. It's exactly what's happening with the indigenous community. In some cases, young children will learn the language as mother tongue, but in many other communities, they won't learn it. If you look at the age structure of the mother tongue, because the language is not being transmitted through generations, and if you track this over time, you will see the pyramid change dramatically and sometimes completely reverse.
On April 19th, 2018. See this statement in context.