The fertility rate decline is driven entirely by millennial mothers in their teens and twenties.
Birth rates for all age groups of women under 30 fell to record lows in 2016.
Immigrant millennials, are also responsible for the drop, the report claims.
The NPG study states that between 2007-2016, the national fertility rate (births per 1000 women, between the ages 15-44) fell from 69.3 to 62.0.
It adds that during the 'baby boomer' era, in the year 1960, the rate was 118.0.
By comparison, the United Kingdom (which also has its own generation of millennials), the total fertility rate from 2000-2016 has actually increased from 1.63 to 1.82, according to data that the NPG took from the CIA, The World Factbook.
'Rites of passage'
The report suggests that multiple 'rites of passage' are being delayed, which has a knock on effect on the years that people choose to have children.
Rites such as moving out of your parent's home and marriage are reportedly being delayed, or given up on altogether.
It explains the shift on the poor economy, and the job losses that millennials witnessed during their formative years (such as the 2008 crash), which deter them from starting their own families.
Millennials came of age during the worst economic crisis since the Great Depression.
Many saw their parents lose their jobs, their homes, and their dignity – and vowed they would not repeat those mistakes.
The report continued;
As a result, life-cycle milestones so prized by their Baby Boomer parents – the first driver’s license, marriage, children, home-ownership – are postponed, or abandoned altogether, by millennials.
The NPG also cites a survey conducted by the Wharton School of Business. It found that 58 per cent of female undergraduates did not plan to have children.
This was in contrast the generation of undergraduates surveyed in 1992, of whom 22 per cent said they did not plan to have children.
According to their website, the NPG is committed to finding an 'optimal' population for the US, using levers such as a 'two-child policy' and controls on inbound immigration to the US.
NPG, Inc. is unique among national organizations in calling for a turnaround in population growth and describing the means to achieve it.
The report has received coverage in the media, which in turn has been poorly received on social media:
@ypulse 1/ Counterpoint: Baby Boomers destroyed the environment making millennial a question whether having kids is ethically viable.
— David Friedlander (@David Friedlander)
@ypulse OR "Millennials introducing reasonable family sizes in response to their grandparents' overbreeding."