A new research made by Joni Hersch, from Vanderbilt University in Nashville, Tennessee, professor of law and economics, revealed that legal immigrants in the United States with a lighter skin color received heavier pay packets than those with darker skin.

Hersch used data from 2,084 men and women, recent immigrants, who participated in the 2003 US government New Immigrant Survey.

In face-to-face interviews, the person's skin color was assessed using an 11-point scale where 0 represented the absence of color and 10 represented the darkest possible skin color.

Even when Hersch took into account factors that might affect wages, such as English language fluency, occupation, work experience and education, she discovered immigrants with the lightest skin color earned, on average, 8 percent to 15 percent more than immigrants with darker skin color. The factor skin color persisted even amongst immigrants with the same ethnicity, race and country of origin.

One more point of lightness on the scale was equivalent to one extra year of education in payment level. Hersch also investigated a link between height and salary. "There's a common saying that all US presidents are tall, and immigrants tend to be shorter on average than Americans," she explains.

Indeed, in the case of immigrants, each extra inch in weight correlated to 1 % more wages.

Hersch searched explanations for the skin color's role on wages, like discrimination in the native country, association of darker skin to outdoor work, which is paid less, and interviewer bias; but after ruling out all these factors, she found discrimination as the most powerful explanation. "I was surprised and dismayed at how strong and persistent the skin color effect was even after I considered a whole series of alternative interpretations and explanations," said Hersch.

"There are well-known differences in salary based on race and country of origin, but I was surprised that, even after accounting for these, skin colour still had an independent effect," says Hersch.

"The findings could support the growing number of lawsuits brought on the grounds of color, rather than racial discrimination," she says.

But currently, such cases rarely bring off.