One in five adults in Michigan doesn't have children and isn't planning on starting a family any time soon.

Regardless of fertility, childfree adults have decided to opt out of parenthood entirely.

"We estimate 21.64 percent of Michigan adults are #childfree," Michigan State University (MSU) sociologist Zarchary Neal wrote in a tweet about the study.

He's the lead author of these new findings, along with research psychologist Jennifer Watling Neal, also at MSU.

The pair set out to determine how many American adults are choosing to live childfree, when childfree adults are making this decision, and if they stuck to it in the long term.

The results offer "critical insights on childfree adults, who are a demographically significant segment of the population, but whose numbers have been substantially underestimated in the past," the authors write.

That underestimation is due to previous studies focusing only on women or relying on data that is not representative of the broader population. For instance, previous fertility-based estimates put childfree prevalence between roughly 2 and 9 percent.

In childfree women under 40, researchers found that deciding to live childfree was particularly common, with 30 percent of women of childbearing age identifying as such (rather than being undecided or ambivalent about having kids).

"Women who decided to be childfree in their teens [and twenties] are now, on average, nearly 40 years old and still don't have children," Watling Neal said.

"And, no, women don't change their mind," Neal tweeted. On average, the childfree women recorded in this study have stuck to their decision for nearly two decades.

If their figures for both men and women hold nationwide, Neal said, it means there could be between 50 and 60 million childfree Americans.

This study acknowledged that people who want to adopt or become stepparents are not childfree, and excludes these groups from their definition of childfree adults.

The study used survey data from 1,500 Michigan-based adults collected in September 2021 and was designed to be representative of the US overall. The survey captured a swath of demographic factors such as age, gender, race/ethnicity, and education, to presidential votes, interest in news, political ideology, and even born-again Christian identification.

The state of Michigan is in fact demographically similar to the entire US population, according to census data, so these findings may indeed indicate nationwide trends.

These trends are illuminating as to the reproductive choices of Americans who, in some states, are now facing restricted access to reproductive healthcare.

"Following the US Supreme Court's overturning of Roe v. Wade, a large number of Americans are now at risk of being forced to have children despite not wanting them," Watling Neal said.

The authors write that when childfree people who request surgical procedures for birth control are denied due to doctors' fears that they may change their mind later is "misinformed" and "paternalistic".

The survey also asked childfree adults and parents how they felt about each other, revealing some tension between groups.

The survey asked individuals to select a number from 0 to 100 with 0 being "very cold or unfavorable" and 100 being "very warm or favorable".

Childfree adults feel similar levels of 'warmth' towards other childfree adults as they do towards parents, and parents feel a similar 'warmth' level towards childfree adults.

However, parents showed a higher degree of favoritism for their own kind.

The researchers suggested the needs of this large – and potentially growing – group are overlooked by US politicians, who often develop policies designed to support parents and children.

"Many people may be at risk of the previously documented negative outcomes experienced by childfree adults, including exclusion from work-life balance considerations, denial of medical care, and attribution of negative stereotypes," the authors write.

The researchers hope revealing the true prevalence of the childfree lifestyle will lead to better representation, reduce stigma, and highlight to young adults that choosing to be childfree is in fact quite common.

This study was published in Scientific Reports.