Walton's research has had a particularly dramatic effect on students' achievement, especially for minority students and women in overwhelmingly male-dominated majors, who may suffer from the dreaded minority achievement gap: the disparity in academic performance that often persists between minority and disadvantaged students and their white counterparts.

CNN: The importance of belonging

Liu has sounded themes of economic disparity on the campaign trail, noting that the income gap between the city's rich and poor has grown in recent years, and he also has emphasized his grasp of the city's finances as comptroller and a trained actuary.

WSJ: Big NYC public-employee union picks Liu for mayor

The gap between rich and poor has slightly narrowed under Lula's administration, but the disparity remains huge.

NPR: Brazil Votes in Runoff to Choose President