The number of women in the United States who are childless is at an all-time high. New research from Kansas State University suggests it may be due to the country's economic downturn.

Recent data from the U.S. Census Bureau's Current Population Survey found that nearly half of women between the ages of 15 and 44 are childless, the highest percentage since the Census Bureau started measuring it in 1976. Previous research has found that an individual's early environment is critical to defining their fertility intentions, but there is little research on how changes in the country's current environment affects those fertility intentions.

"There's a life history theory that suggests where you grew up plays a key role in defining your fertility intentions," said Lora Adair, 2015 doctoral graduate in psychological sciences, Crestview, Florida. "Individuals who grow up in a relatively resource-poor, high-mortality environment tend to have more kids at an earlier age -- and women in those environments even menstruate sooner. People who grow up in a relatively resource-rich, low-mortality environment tend to have fewer kids and at a later age so they can pursue other things like going to college and building an economic, career-based legacy before they have kids."

Adair's dissertation, "Family Planning in Context: Sensitivity of Fertility Desires and Intentions to Ecological Cues," sought to find out how these individuals respond to new information about their environment, and if women's changing economic status gives them more decision-making power when it comes to having children.

In her research, Adair exposed individuals from different socioeconomic backgrounds to information suggesting a change in their current environment. These changes included an increase in mortality rates -- seemingly unmotivated homicides -- and an increase in economic instability, or an economic downturn. What she found was somewhat surprising.

"People raised in different environments tend to respond differently to that kind of information," Adair said. "People raised in relatively resource-poor environments indicated they would have more children and have them sooner when presented with information about an increase in mortality rates. Contrary to predictions, people raised in resource-poor environments indicated they would have fewer children and delay having children when presented with information that economic conditions have changed for the worse. Those raised in resource-rich environments didn't change their fertility intentions when provided new information."

Adair believes these different decision-making strategies may be based on different world perceptions, with those in a lower socioeconomic environment thinking bad conditions are unpredictable and persistent, whereas people in higher socioeconomic conditions recognize the new information as predictable and temporary.

Her research also found no gender difference in fertility decision-making power. She evaluated 60 couples as they discussed their family planning intentions. She found both men and women equally use concessions, compromise, persuasion, agreement or disagreement when deciding to have children.

"There is a sociological perspective that suggests women's social, economic and political power changes in Western society are leading toward a more egalitarian society and as women gain in this power, the fertility decision moves from being male-dominated to female-dominated," Adair said. "However, my study shows the power is not shifting hands, but becoming more equal. Men and women were weighing in equally to this big life decision."

As America's dynamics and social structures continue to change, Adair believes these environmental factors contribute to changing fertility desires, and could be contributing to the low fertility rates.

"The information you expose people to matters," she said. "Our fertility intentions aren't necessarily just something you're born with; it's a highly malleable thing that changes in response to whether you grow up in an environment seeing resources as something you can rely on, or in one that sees them as something that's highly variable. When you're confronted with new information suggesting your current environment is unreliable, that can completely change the way you see your future in terms of having children."