How can the Latino population be growing rapidly while Spanish-speaking remains stable? The answer lies in oft-overlooked peculiarities of census data and in the particular linguistic history of the United States.
If one looks only at immigration patterns over the past half-century, it is true that the U.S. has been gaining Spanish-speakers. From 1965 to 2015, roughly half of all immigration has come from Latin American countries. This trend added some 30 million people [pewhispanic.org], most of whom came speaking Spanish, to the American populace.
But this is only half the story. While new immigrants bring Spanish with them, research shows [wikispaces.com] that their children tend to become bilinguals who overwhelmingly prefer English [pewresearch.org]. As a result, the same immigrants' grandchildren likely speak English only.
Linguists call this phenomenon "the three-generation pattern [princeton.edu]." In essence, it means that non-English languages in the U.S. are lost by or during the third generation.
We can see this pattern playing out in data from the Pew Hispanic Center [pewresearch.org]. Surveys show that in 2000, 48 percent of Latino adults aged 50 to 68 spoke "only English" or "English very well," and that 73 percent of Latino children aged 5 to 17 did.
By 2014, those numbers had jumped to 52 percent and 88 percent, respectively. In other words, the shift from Spanish to English is happening nationwide, both over time and between generations.
If the preferred language is English, why do the immigrants refuse to understand common English terms like "taco," "burrito," "loco," and "amigo?"