移民们正在维持美国的出生率免于下降。
That information comes from a new study. The Pew Research Center, an independent research group, reported the finding.
该信息出自一项新的研究。皮尤研究中心是一家独立的研究组织，该组织报告了这一发现。
According to the study, U.S.-born women gave birth to 3.10 (million) babies in 2014. That is down from the 3.46 million born in 1970.
根据这项研究，2014年生于美国的女性生下了310万个婴儿，低于1970年生育的346万人次。
Since that year, births to immigrant women have jumped by more than 300 percent. It reached 901,000 births in 2014.
自那年起，移民女性的生育人数增长了300%以上，2014年生育人数达到了90.1万。
More Babies Born to Asian Immigrants
更多婴儿由亚洲移民所生
Pew's researchers say more than half of the foreign-born mothers are from nine countries and one U.S. territory. Those countries include Mexico, China, India, El Salvador, Guatemala, and the Philippines. Also on the list are Honduras, Vietnam, Dominican Republic and Puerto Rico.
皮尤研究中心的研究人员表示，一半以上在外国出生的母亲来自9个国家和一处美国领地。这些国家包括墨西哥、中国、印度、萨尔瓦多、危地马拉和菲律宾。此外还有洪都拉斯、越南、多米尼加共和国以及波多黎各（美国领地）。
Asian immigrants now represent 22 percent of U.S. births by foreign women, up from 16 percent in 2010, the Pew study found.
皮尤研究中心的这项研究发现，亚洲移民占到了在美国生育的外国女性的22%，高于2010年的16%。
It is not just that there are more immigrant women living in the United States. Foreign-born women are having more children than U.S.-born women, Pew said.
皮尤研究中心表示，这不仅仅是因为有更多移民女性居住在美国，还因为在外国出生的女性比在美国出生的女性生育更多孩子。
In 2014, there were 58.3 births for every 1,000 U.S.-born women of childbearing age. The number is 84.2 per 1,000 foreign-born women.
在2014年，每1000名在美国出生的育龄妇女生下了58.3个孩子，而每1000名在外国出生的育龄妇女生下了84.2个孩子。
Birth Rates Down Generally
出生率普遍下降
Birth rates for both U.S.-born and foreign-born women are down since 1970. But the 2014 rate for foreign-born women is similar to the rate for U.S.-born women 40 years ago, Pew said.
皮尤研究中心表示，在美国出生和在外国出生的妇女的生育率从1970年开始都有所下降。但是2014年在外国出生的妇女的生育率和40年前的在美国出生的妇女的生育率接近。
The drop in total fertility rates has been sharp since the economic recession of 2008, according to the U.S. Census Bureau. The term total fertility rates mean how many children the average woman will have in her lifetime.
美国人口普查局表示，自2008年经济危机以来，总生育率急剧下降。总生育率是指平均每名妇女一生之中会生下多少个孩子。
Among immigrant women, the fertility rate dropped from 2.7 in 2008 to 2.2 in 2014, the Census Bureau said. For American-born women, the rate dropped from 2.1 to 1.8.
美国人口普查局表示，移民妇女的总生育率从2008年的2.7下降到了2014年的2.2。而在美国出生的妇女的总生育率从2.1下降到了1.8。
According to the Pew report, 51 percent of foreign-born mothers spent at least 11 years in the United States before having a baby. Just nine percent had arrived less than two years earlier, it said.
根据皮尤研究中心的报告，51%在外国出生的妇女在生育前至少已经在美国呆了11年，只有9%在外国出生的妇女到美国不到两年就生育。
The report found that 275,000 babies were born to undocumented immigrants in 2014.
该报告发现，2014年有27.5万名婴儿是由非法移民所生。
William Frey is with the Metropolitan Policy Program at the Brookings Institution in Washington, D.C. If it were not for immigrants, Frey said, the U.S. birth rate would be much lower and that could result in shortages of workers.
威廉·弗雷(William Frey)就职于华盛顿布鲁金斯学会的大都市政策项目组。弗雷表示，若不是移民，美国的出生率会更低，这会导致劳动力短缺。
"My view is that we actually need more young people in this country and that immigrants and their children are going to fill that need," Frey said.
弗雷表示，“我的看法是，美国需要更多年轻人，而移民和他们的孩子将会填补这种需求。”
Steven Camarota is director of research for the Center for Immigration Studies in Washington. The center supports calls to limit immigration.
史蒂文·卡马罗塔（Steven Camarota）是华盛顿移民研究中心的研究主任。该中心支持限制移民的呼吁。
Camarota said it is true immigrants are generally young. That means they can fill jobs and help support programs that provide health and retirement assistance for older Americans.
卡马罗塔表示，移民一般都很年轻，这是事实。这意味着他们可以填补工作岗位，并帮助维持为美国老年人提供医保和退休金的项目。
Those retirement programs are projected to run short of money in coming years as more Americans grow older and leave the workforce.
这些退休项目预计在未来几年将会缺少资金，因为越来越多美国人变老并离开职场。
But Camarota said immigrants also generally earn less money than native-born Americans and, as a result, use more social welfare programs. That takes tax money away from other services, he said.
但是卡马罗塔表示，移民一般来说也比本土出生的美国人赚得少，因此会占用更多的社会福利项目。他说，这剥夺了用于其它服务的税款。
He added that lower birth rates for immigrants are offset by higher yearly immigration totals.
他补充说，移民的低出生率被更高的年度移民总数所抵消。
Fewer Unmarried Women Having Babies
未婚产子减少
The Pew Research Center report also reported a drop in the percentage of births to unmarried foreign-born mothers. It is down from 37 percent in 2008 to 33 percent in 2014.
皮尤研究中心的这份报告还称，在外国出生的未婚妈妈的生育百分比有所下降，该百分比从2008年的37%下降到了2014年的33%。
At the same time, the rate has held steady for U.S.-born women, Pew reported. It now stands at 42 percent.
皮尤研究中心表示，与此同时，对于在美国出生的妇女来说，这一比例保持了稳定，该比例目前为42%。
I'm Bruce Alpert.
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