Are teachers' impacts on students' test scores ("value-added") a good measure of their quality? This question has sparked debate largely because of disagreement about (1) whether value-added (VA) provides unbiased estimates of teachers' impacts on student achievement and (2) whether high-VA...

In this paper--the first in a series of two papers that use data on 21 billion friendships from Facebook to study social capital--we measure and analyze three types of social capital by ZIP code in the United States: (i) connectedness between different types of people, such as those with low vs....

Low levels of social interaction across class lines have generated widespread concern and are associated with worse outcomes, such as lower rates of upward income mobility. Here, we analyze the determinants of cross-class interaction using data from Facebook, building upon the analysis in the...