For generations, Americans have thought of themselves as part of a dynamic, innovative and ever-expanding country, with an almost limitless horizon. In recent weeks, they have seen a portrait of a different nation, one that challenges assumptions about America as a land of continuing growth and unlimited opportunity.

On April 26, the Census Bureau reported that in the last decade the U.S. population grew at its slowest rate since the Great Depression, and the second-slowest rate for any 10-year period since the nation’s founding. Last week, the government reported that the nation’s birthrate had declined for the sixth straight year, including a precipitous drop in births in December, adding up to fertility rates too low to keep the country’s population growing by births alone.

To demographers and others who study these trends, the official figures were not a surprise, merely confirmation of patterns visible for some time. Nor are they unique to the United States. Other industrialized nations from Japan to those throughout Europe have been facing the same or worse for years. But coming as they did in rapid succession — and with the imprimatur of the decennial census on the slowing population growth — the numbers amounted to a blinking light about the path ahead.