The researchers conclude that this difference cannot be accounted for by increases in food intake or other lifestyle factors such as socioeconomic status, smoking or alcohol.

BBC: Starved babies 'become obese adults'

Critics of race-based admissions question whether educational institutions would serve the goals of affirmative action better by relying exclusively on non-race based criteria, such as socioeconomic status and family educational history.

FORBES: Why It's a Mistake for Doctors to be Color Blind

The changes could not be explained by other factors - such as mother's age and socioeconomic status or population effects such as changes in air pollution and influenza epidemics.

BBC: Smoking ban 'cuts premature births'

Even after the researchers accounted for factors that could affect rates of allergies, such as race or ethnicity and socioeconomic status, the strong association between being born in the United States and the higher risk of allergic diseases remained.

CNN: American kids have higher allergy risk

Researchers in virtually all countries have identified strong correlations between various educational outcomes and socioeconomic status (SES) as measured by factors such as family income and parental education.

UNESCO: II Part Analytic Section