Deaths exceeded births among non-Hispanic white Americans for the first time in at least a century, according to new census data, a benchmark that heralds profound demographic change.

The disparity was tiny — only about 12,000 — and was more than made up by a gain of 188,000 as a result of immigration from abroad. But the decrease for the year ending July 1, 2012, coupled with the fact that a majority of births in the United States are now to Hispanic, black and Asian mothers, is further evidence that white Americans will become a minority nationwide within about three decades.

Over all, the number of non-Hispanic white Americans is expected to begin declining by the end of this decade.

“These new census estimates are an early signal alerting us to the impending decline in the white population that will characterize most of the 21st century,” said William H. Frey, a demographer with the Brookings Institution.