Answer by taking a quote from the following article:

Indigenous peoples of Mexico (Spanish: pueblos indigenas de Mexico), Native Mexicans (Spanish: nativos mexicanos), or Mexican Native Americans (Spanish: nativo america mexicanos), are those who are part of communities that trace their roots back to populations and communities that existed in what is now Mexico prior to the arrival of Europeans. According to the National Commission for the Development of Indigenous Peoples (Comision Nacional para el Desarrollo de los Pueblos Indigenas, or CDI in Spanish) and the INEGI (official census institute), in 2015, 25,694,928 people in Mexico self-identify as being indigenous of many different ethnic groups, which constitute 21.5% of Mexico's population.

The Law of Linguistic Rights of the Indigenous Languages recognizes 62 indigenous languages as "national languages" which have the same validity as Spanish in all territories where they are spoken. According to the National Institute of Statistics, Geography and Data Processing (INEGI), approximately 6.7% of the population speaks an indigenous language. That is, less than half of those identified as indigenous. 6,695,228 people 5 years or older were tallied as indigenous-language speakers in the 2010 census, an increase of about 650,000 from the 2000 census. In 2000, 6,044,547 people 5 years or older spoke an indigenous language.  In previous censuses, information on the indigenous speaking population five years of age and older was obtained from the Mexican people. However, in the 2010 census, this approach was changed and the Government also began to collect data on people 3 years and older because from the age of 3, children are able to communicate verbally. With this new approach, it was determined that there were 6,913,362 people 3 years of age or more who spoke an indigenous language (218,000 children 3 and 4 four years of age fell into this category), accounting for 6.6% of the total population. The population of children aged 0 to 2 years in homes where the head of household or a spouse spoke an indigenous language was 678 954. The indigenous language speaking population has been increasing in absolute numbers for decades, but have nonetheless been falling in proportion to the national population.  The recognition of indigenous languages and the protection of indigenous cultures is granted not only to the ethnic groups indigenous to modern-day Mexican territory, but also to other North American indigenous groups that migrated to Mexico from the United States in the nineteenth century and those who immigrated from Guatemala in the 1980s.

What did the government do with this data collected ?
indigenous language speaking population has been increasing