, Alicia Shields - Fotolia

Parents can be bombarded with conflicting messages about what's best for kids when it comes to family size. There's no dearth of studies that chime in on the topic. The good news is research always paves the way for creative thinking about how to get good results despite challenges.

Here's a sampling of what research has found about family life through the lens of the number of children parents have.

  • Pew Research Center said the perception of what’s an ideal family size in America is shrinking. In 1971, the most popular number of kids switched from four to two and there it has remained.
  • Among well-educated women, however, childlessness is dropping and the number of children may be on the rise, says another Pew Research study.
  • A recent study in The Economic Journal also suggests women with more education and money may be choosing to have more children, in part because they can afford the children and support services to help them. Historically, highly educated women with better income have had fewer children, compared to poorer, less-educated women.
  • Researchers from the University of Houston find a “quality-quantity” trade-off around family size. The paper, published by the National Bureau of Economic Research, says after a new sibling is born, older boys tend to have behavioral problems, while older girls earn lower math and reading scores.
  • Birth order doesn’t impact intelligence, but family size may, according to a 2012 study from the London School of Economics and Politics published in the Personality and Social Psychology Bulletin. Data on 17,000 people linked smaller family size to greater intelligence in children.
  • Economics influences family size more than other considered factors, said 2013 research from the University of Missouri-Columbia. Getting more education, creating jobs and the move away from agriculture improve the standard of living and correlate to declining fertility rates, according to a written statement on the study.
  • A 2006 Ohio State University study contradicted previous suggestions that older children are smarter than their younger siblings. "Birth order may appear to be associated with intelligence, but that's only because larger families don't have the advantages of smaller families," said Aaron Wichman, lead author of the 2006 study, in a news release. The study was published in Personality and Social Psychology Bulletin.
  • A 2010 study of British and American kids found male children, kids with health issues and those with divorced moms at increased risk of behavioral problems. Family size had different impacts: In Great Britain, the more children, the greater the likelihood a child had behavioral problems, but not in America, said the American Sociological Association.
  • There’s no strong link between family size and a finding that reading challenges and behavior problems are “intertwined” for boys, according to a 2006 study in the journal Child Development.
  • Australian researchers who looked at the impact of China’s one-child policy concluded that “individuals who grew up as single children as a result … were significantly less trusting, less trustworthy, more risk-averse, less competitive, more pessimistic, and less conscientious individuals,” they said in a 2013 news release. The study, in Science, said effects were not corrected by socialization efforts.
  • Siblings help shape each other, according to a 2010 issue of New Directions for Child and Adolescent Development. Researchers at the University of Illinois said good sibling relationships improve outcomes when it comes to delinquency, teen pregnancy, smoking, drinking and more.

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