World population grew by 75 million in past year

The growth rate for the United States in the past year was 0.53%, about half the worldwide figure. The U.S. added 1.7 million people and will have a population on New Year's Day of 335.8 million people.

If the current pace continues through the end of the decade, the 2020s could be the slowest-growing decade in U.S. history, yielding a growth rate of less than 4% over the 10-year-period from 2020 to 2030, said William Frey, a demographer at The Brookings Institution.

The slowest-growing decade currently was in the aftermath of the Great Depression in the 1930s, when the growth rate was 7.3%.

"Of course growth may tick up a bit as we leave the pandemic years. But it would still be difficult to get to 7.3%," Frey said.

At the start of 2024, the United States is expected to experience one birth every nine seconds and one death every 9.5 seconds. However, immigration will keep the population from dropping. Net international migration is expected to add one person to the U.S. population every 28.3 seconds. This combination of births, deaths and net international migration will increase the U.S. population by one person every 24.2 seconds.