(Agencies)
Updated: 2008-01-16 22:02

To many economists and policymakers, the increase in births is good news. The US fertility rate -- the number of children a woman is expected to have in her lifetime -- reached 2.1. That's the "magic number" required for a population to replace itself.

Countries with much lower rates -- such as Japan and Italy, both with a rate of 1.3 -- face future labor shortages and eroding tax bases as they fail to reproduce enough to take care of their aging elders.

But the higher fertility rate isn't all good. Last month, the CDC reported that America's teen birth rate rose for the first time in 15 years.

The same report also showed births becoming more common in nearly every age and racial or ethnic group. Birth rates increased for women in their 20s, 30s and early 40s, not just teens. They rose for whites, blacks, Hispanics, American Indians and Alaska Natives. The rate for Asian women stayed about the same.

Total births jumped 3 percent in 2006, the largest single-year increase since 1989, according to the CDC's preliminary data.

Clearly, US birth rates are not what they were in the 1950s and early 1960s, when they were nearly twice as high and large families were much more common. The recent birth numbers are more a result of many women having a couple of kids each, rather than a smaller number of mothers, each bearing several children, Astone said.

Demographers say there has been at least one boomlet before, around 1990, when annual US births broke 4.1 million for two straight years before dropping to about 3.9 million in the mid-1990s. Adolescent childbearing was up at the time, but so were births among other groups, and experts aren't sure what explained that bump.

The 2006 fertility rate of 2.1 children is the highest level since 1971. To be sure, the fertility rate among Hispanics -- 3 children per woman -- has been a major contributor. That's the highest rate for any group. In 2006, for the first time, Hispanics accounted for more than 1 million births.

The high rate probably reflects cultural attitudes toward childbirth developed in other countries, experts said. Fertility rates average 2.7 in Central America and 2.4 in South America.

Fertility rates often rise among immigrants who leave their homelands for a better life. For example, the rate among Mexican-born women in the US is 3.2, but the overall rate for Mexico is just 2.4, according to the Pew Hispanic Center, a Washington-based research organization.

"They're more optimistic about their future here," said Jeff Passel, a Pew Center demographer.

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