In 2012, the U.S. population was approximately 309 million. About 20.6 million, or 6.6 percent, are children in the 10 to 14 age range, and 21.2 million, or 6.9 percent, are in the 15 to 19 age range. The margin of error is near 30,000. As of 2012, another 40 million children are newborn to age 9, which is about 13 percent of the population.