Story highlights Fertility rate is at the lowest recorded number in history

Women are having children at an older age, when the chance of fertility is lower, experts say

(CNN) The US fertility rate has dropped to the lowest number reported since fertility records started being kept more than a century ago. There were 61.5 births per 1,000 women aged 15 to 44 in the year ending the first quarter of 2017, according to numbers released by the National Center for Health Statistics on Tuesday.

This demonstrates a further decline from the previous year; at the same point in 2016 , the rate was 62.5 births per 1,000 women. The report states the shift from last year to this year is significant, meaning the difference is more than experts would expect mere chance to produce, said Brady Hamilton, a statistician-demographer with the center and an expert on fertility data.

The general fertility rate gives an idea of how many children are being born into the population during a specific period, he said. These numbers can be monitored to assess levels of reproduction within a population over time.

"When it comes to births, it tells us about future members of society that will go on to replace the current work force and will be generating revenues and so on," Hamilton said. "So this information allows you to see how the United States has changed demographically. It allows you to see where you currently stand."

It is important to remember that although the country is at record lows in fertility, there is also a large influx of immigrants, Hamilton said. This will affect the population number, taxes and demand for education.

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