A new report from the Pew Hispanic Center says a lot about the assimilation of the nation’s largest minority group — both good and bad. Hispanics — those 50 million people who trace their ancestry to a Spanish-speaking country — have become both more numerous and more diverse in the past 40 years. In 1970, Hispanics were primarily U.S.-born Mexican-Americans and Puerto Ricans — who are U.S. citizens, whether born in Puerto Rico or on the mainland. But the adult population of Hispanics today is almost equally divided between those who were born in the U.S., 48 percent, and those who are foreign-born, 52 percent.

Unsurprisingly, the presence of this large immigrant group is affecting the way Hispanics think of themselves. One aspect of the report that is bound to provoke controversy — and, in some quarters, resentment — is how few Hispanics identify themselves first and foremost as Americans. Only 8 percent of immigrants, 35 percent of second-generation Hispanics and 48 percent of third-generation Hispanics do, according to the Pew study. The question is, Why?