The U.S. Census Bureau released data in January 2012 with sobering implications: The bad economy and slowdown in immigration are shrinking the numbers of children in the U.S. for the first time in a generation. The number of people under 18 was 73.9 million on July 1, 2011. That is a decline of 260,000 from the previous year. Overall, the U.S. population is growing at its slowest rate since the mid-1940s.